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

Where the floorpan sits over the inner floor supports, the floor will require holes to be drilled for more plug-welds. Transfer the floor-support location to the floorpan with a scribe or permanent marker...

...then drill through the floorpan to expose the inner floor support for welding. Don't drill through the inner floor support itself.

The floorpan's welding is now complete. As you can see, there are numerous plug-welds...

...to secure the pan to the inner rails, floor supports, and more.

The seat risers included with the floorpan kit are a thicker-gauge steel than the floorpan itself...

so the hole-punching tool won't work, and a drill will be required.

While the floorpan and riser are E-coated...

...a layer of primer before welding will help inhibit future corrosion in the area.

Don't forget to install the rear seat-base retaining brackets. The Dynacorn kit includes new brackets for most applications, but for our '66 fastback, we reused the originals.

Without these, the rear-seat base wouldn't lock into place, so be sure to install them before moving forward with your interior reassembly.

With welding complete, the plug-welds are dressed with a grinder. The welds need to be dressed down only enough to take off any welding slag and make for a uniform finish. Grinding them too far weakens the weld.

In any sheetmetal repair, the seams of the repair panels must be closed with seam sealer.

The factory brushed it on, pushing it into the seam.

You can easily replicate that look, even with tube-applied seam sealer, by brushing the bead of caulk with a small disposable acid brush.

After the seam sealer has cured...

...the completed repair is painted and the body is ready to head into the paint booth...

...for a fresh coat of Wimbledon White.