The Harrison’s Rod & Custom ’71 GMC, Part 1

By Bryan Harrison   –   Photography by the Author

This is the ’71 GMC 1/2-ton Stepside owned by my Uncle Jack Fillers from Greeneville, Tennessee. It was originally a 292 inline-six with a TH350 transmission and a 12-bolt 3:73 rear. It has had one obvious repaint in its life where the bumpers were painted the Factory 504 Medium Olive Metallic. The original wood bed floor was pretty much gone and it had some minor cab corner/rocker rust that needed to be replaced. The project was the result of a conversation in my booth at the NSRA Street Rod Nationals in Louisville, Kentucky, between Jim Ries and myself about whether we’d be willing to work with CTP and Jim’s company, Classic Performance Products (CPP), to do some articles showcasing product. Since we’d already been using CPP in the shop it seemed like an easy answer and numbers were exchanged to move forward.

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02 1971 GMC Truck green paint

It was March 2022 on a Sunday afternoon when Uncle Jack calls me wanting to forward me a link to a marketplace ad for a ’71 GMC in Danville, Virginia. After having a look myself, I advised Uncle Jack he’d better get the guy on the phone because the truck wouldn’t last long. A man’s good word to hold the truck until early Wednesday morning, a few hours pulling an empty trailer, and we were in Virginia laying eyes on the truck. Uncle Jack, who was standing above as I looked underneath, was waiting for my assessment. After I gave him the nod, I was tilting the trailer to load up while Uncle Jack paid the seller who then informed us that a guy, who’d driven from Arkansas, was in a local hotel waiting to buy the truck if we declined. The seller had kept his word to hold the truck, without a deposit, until we came to look at it, which is a true testament to the folks we meet in the truck community. Unfortunately for the man from Arkansas who went home empty-handed, but fortunately for us we went home loaded and began making calls to get a plan in place.

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03 1971 GMC Truck step side

I contacted Auto Metal Direct’s (AMD) Jason Chandler on the drive home to inform him of Uncle Jack’s purchase and our need for new chrome and various other pieces. AMD has supported Harrison’s Rod & Custom with quality parts for pretty much everything we work on for several years. This project was no different and bumpers, brackets, hardware, grille, glass, and inner fenders were on their way before the truck was home.

04 1971 GMC Truck rusted frame

The next call was to CPP’s Sadie Ries who, in keeping with CPP’s word, got us with the proper people there to get our suspension, steering, and other chassis items en route. They contributed a full coilover suspension with all tubular control arms, sway bar, large-diameter four-wheel disc brakes with master cylinder, related e-brake components, 500 Series power steering conversion, and their tilt steering column. We also utilized their engine mounts for the small-block swap, transmission crossmember, and trailing arm crossmember to keep our geometry right with the drop and be able to pass the exhaust through it, keeping it above the bottom of the truck where it’s better heard than seen.

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05 1971 GMC Truck frame repair

We also added parts from Cold Case Radiators, Classic Instruments, Vintage Air, Powermaster, American Racing, Sanderson Headers, Quick Fuel, Optima, Kicker, Memphis Audio, Auto Custom Carpets, American Autowire, and MagnaFlow to bring you one completely transformed ‘71 GMC with just enough flash to offset its perfectly flawed exterior and give Uncle Jack an easy-driving, reliable, real-world “Traditional Hot Rod Truck Style” truck he can enjoy without the stress associated with actually driving and enjoying a fully slicked up truck.
06 1971 GMC Truck cutting frameSuspension

The first order of business out back was to create room for the axle to live right once the drop was achieved. Since I like to run thick sidewall back tires, we tend to need more drop to get the truck down over them. I use a Hypertherm Plasma Cutter for the bitch cutting to keep cuts clean and eliminate overlapping cut lines that can lead to trouble later.

07 1971 GMC Truck new frame

Once safely in the air and supported, an air chisel was used to remove the factory center trailing arm crossmember for the install of the CPP unit which corrects the “droop” of dropped trailing arms and gives the exhaust some holes to pass through. We’ll be needing those for the 2.5-inch MagnaFlows later. The chassis was stripped, prepped, and painted before final assembly.

08 1971 GMC Truck new suspension mounts

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To achieve the desired drop, as well as maintain the ride quality, we used the CPP rear coilover setup with Viking double-adjustable shocks. The fit on the kit was fantastic and the installation was a breeze. Everything fit as it should and began to really dress up the rear chassis.

09 1971 GMC Truck power steering upgrade

The fit and heavy-duty nature of the CPP center member really did a lot to make a solid foundation for the suspension to come. When the desired result is to get low, with a livable ride and geometry, the CPP center member made a marked difference in stiffening up the frame.

10 1971 GMC Truck frame mounts

Once paint was complete, the CPP 500 Series power steering conversion and tubular coilover suspension was installed per the directions. The front also uses the Viking double-adjustable shocks. All-new tie rods were installed, and billet tie rod adjusters were also used to keep the alignment adjusting simple and trouble-free. The CPP front big brakes were installed and the truck was on the ground for the first time on its 18/20-inch American Racing VN215 Torq Thrusts.

11 1971 GMC Truck upper and lower control arms

The finished chassis is clean and detailed yet still usable with durable finishes that can be cleaned. The transmission got Fragola AN lines to the cooler, as well as an aluminum pan that has a convenient drain for service.

12 1971 GMC Truck suspension hardware

Brakes

A simple remove-and-replace of the master cylinder using the CPP unit with included proportioning valve put the brake lines exiting perfectly for a well-entailed result. It was easy to adjust up for proper brake bias, too. The fins were great and it bled up quickly, partly due to properly bench bleeding the master cylinder first. Push rod adjustment was quick and easy.

13 1971 GMC Truck coil overs

The front CPP Big Brake kit went on smooth using supplied instructions. The X10 Modular Spindles with the new modular wheel hub assembly is the way to go. No greasing bearings, no castle nuts, or cotter pins. Simply open them up and install them. The preload is right every time. We used CPP stainless hoses then plumbed up the rest with custom bent lines once the master cylinder was in place.

14 1971 GMC Truck new wheel hub assembly

The CPP rear brakes with included e-brake system really installed smoothly with included instructions. The finish and fit were nice and the performance once finished should be out of this world.

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15 1971 GMC Truck suspension and brakes

Steering

Having used CPP 500 Series steering boxes on past projects, we knew that was what we wanted for the ’71. Installation was simple and fitment/finish great. The added billet top plate to finish it off makes it even cooler. The supplied hoses fit good and the pump/brackets aligned perfectly.

16 1971 GMC Truck custom frame

We again used CPP for their steering column. The tilt works great and adds a lot to the room inside. The shifter was connected to a rebuilt TH350 trans with a Lokar Performance ACA-1800 linkage kit. The shifter feels really crisp through the gears and the neatest safety switch/backup light switch adjusted up quickly. The illuminated gear indicator is a really nice touch also.

Source
Harrison’s Rod & Custom
(423) 823-2111

Click on this issue’s cover to see the enhanced digital version of The Harrison’s Rod & Custom ’71 GMC, Part 1.

ctp october 2023

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