Dynacorn's '65-'68 Mustang One-Piece Floorpan - Floor It!

A hammer and cold chisel were also used in some areas to help separate spot-welded panels.

As you remove sections of the floor, be aware that some brackets, such as parking-brake linkage or cable mounts, will need to be drilled out and transferred to the new floor assembly.

With any sheetmetal repair, there will be fringe areas that require the creation and installation of patches. In the case of our floorpan install...

...the passenger-floor-to-firewall area needed a small patch fabricated, while we also had to create a few small patches along the rear transition panel into the trunk.

Once the surrounding metal was ground with a wire wheel and the necessary patches were created and welded in, primer was applied to the bare areas before moving forward with the installation of the rear torque-box tops and test-fitting of the floor itself.

The kit's included rear torque-box tops must be installed before the new floorpan assembly. When MIG-welding the panel, we had to drill a series of holes around the perimeter so that we could plug-weld the top panel to the torque box.

As mentioned before, any parking-brake brackets will need to be transferred to the new floor. Measure the old floor to determine where the various brackets must go; then weld them in the proper location.

As with the torque-box panels, the main floorpan needs to have plug-weld holes created around its perimeter. A hole-punch tool is used for the thinner metal of the floorpan.

The one-piece floor is installed through the open doorway of the unibody, requiring an extra set of hands and the slight bending/flexing of the floor to fit through the opening. We're using Dynacorn PN 3648C for '65-'68 coupes/fastbacks. Other applications are available for '69-'70 models and for convertibles.

A good selection of locking pliers in various lengths and configurations are your best bet when completing sheetmetal repairs such as this. The floorpan must be secured for the proper fit before welding commences. Don't be afraid to massage the floorpan as needed for the best fit possible.

Once you're happy with the fit of the floorpan to the firewall, transition pan, and inner rockers, begin plug-welding the floor into place. To prevent warpage of the floorpan while welding, move from one side of the floor to the opposite side, allowing the previous area to cool.