Replacing the Floor on Your 1964-68 Mustang

By Ron Ceridono – Photography By Tate Radford

When Colin and Sue Radford found this forlorn 1965 fastback Mustang it was obvious that major repairs were needed—being able to see the ground through the floor was one of the first indications of the problems to be dealt with. But the Radfords are not easily discouraged, and they knew everything needed to fix the Ford was available from Golden Star Classic Auto Parts. Based in Texas, Golden Star offers an array of high-quality replacement components for classic cars and trucks from GM, Ford, and Chrysler.

02 1965 Ford Mustang body elevated on jack stands stripped exterior prepared for floor pan replacement — Thanks to Golden Star Classic Auto Parts all the quality replacement sheetmetal necessary to make this Mustang as good as new is available. We’re starting with the floor, but more sheetmetal surgery will come.

There was a time when making repairs to the damaged floor of a project car prompted all sorts of questionable creativity. Over the years, we’ve seen repairs made with license plates, road signs, galvanized sheetmetal, and odd bits of salvaged body parts. Often, these crude repairs were secured over gaping rust holes with a handful of sheetmetal screws. In this case, the previous owner had attempted to make repairs with actual patch panels, but they were installed so poorly that the only way to make things right was to remove the entire floor and start over.

03 Severe rust damage on 1965 Ford Mustang floor pan with exposed wiring and corroded edges — We’ve speculated that a replacement shifter installation hole might have been done with a chainsaw, but we could be wrong.

For unitized construction cars like the Mustang, the lack of a separate frame means the entire body becomes a load-bearing structure. While various supports all add strength, the doorsills, floor, and even the roof are all critical components when it comes to maintaining the rigidity of the body. That means replacing the floor is not only a cosmetic improvement, it’s also a structural repair.

04 Close up of 1965 Ford Mustang rusted floor pan and cut out section during repair — A previous owner had attempted to match the Mustang’s floor with little attention to fitting the replacement sheetmetal. That resulted in a number of gaps that could not be welded.

The Radfords’ grandson, Tate, began the repair process by removing the floor from the toeboards and moving it to the back seat supports. With the floor out of the way, the floor-to-firewall supports were also removed. These simple yet critical pieces tie the car’s floor to the subframes that mount the front suspension.

05 Partially installed patch panel on 1965 Ford Mustang visible welds and restoration in progress — We filed this repair under “What was he thinking?” Another huge hole to be filled; to the left is the damaged floor support that also needed to be replaced.

Reconstruction of the fastback began with installing Golden Star’s replacement floorpan to firewall supports (PN FP20-64FF). Next came the complete floorpan (PN FP20-64) (these floors fit coupes and fastbacks; convertible floors are also available). The integral transmission/driveshaft tunnel and stamped indentations make the sheetmetal extremely rigid and duplicate those features found on the factory floors. The complete floorpan included front seat platforms that mount the seats and reinforce the floor structure.

06 Underbody view of 1965 Ford Mustang freshly welded and coated floor pan patch — Sadly, the welds made were on par with the rest of the work that was done.

Once the floor-to-firewall supports and the entire floor was replaced, the last step was to add a leftside floorpan to the firewall patch panel (PN LH FP20-641L) to replace the previously poorly executed replacement. Only the driver side panel was replaced as the passenger side sheetmetal was solid.

07 Completed floor pan welding on 1965 Ford Mustang detailed seams and solid black finish — In a case like this, a botched repair cannot be saved; the only option is to start over.

When Ford introduced the fastback version of the Mustang in 1965, body style 63A (09), a little over 77,000 were sold. While there is slightly more than the number of convertibles produced that year (roughly 73,000), fastback production dropped in the bucket compared to the over 409,000 coupes sold. The following year, fastback sales dropped to less than 36,000, the lowest production of all models manufactured in 1966 (coupe sales reached almost 500,000, and slightly more than 72,000 convertibles went to buyers).

08 Firewall section of 1965 Ford Mustang stripped and primed ready for reassembly — The floorpan to firewall supports was visible with the floor removed. These supports are critical to maintaining the strength of the unitized body.

Given the probable survival rate of early Mustang fastbacks, it makes sense to save one if possible, and thanks to Golden Star it can be done effectively. With new floor and supports installed, the Mustang’s foundation was solid again and it was no longer possible to see the ground inside the car. Next time, we’ll focus on repairing more of the abuse our ponycar has endured by replacing the quarter-panels. We will reveal a few tricks to make the job easier.