Installing the floor and seat pan
With the frame rails repaired and the rust removed, it’s time to weld back in a floor on the passenger side!
I don’t have any pictures, of the paint and prep, but the floor pan was painted with weldable primer, like pretty much every part of this repair. The next step was to weld on the seat belt anchor bolt. I ordered a new one and welded it in per the Ford weld and sealant manual (See my post on books here) With the floor pan prep complete, it’s time to install.
Once again I test fit the floor pan. Then with a magic marker I traced around the floor support and the transmission mount. and the lower seat pan. I also marked the location for the parking brake cable bracket. I then removed the floor pan and drilled all the spot weld holes. The floor pan attaches to the inner frame rail with about 40 spot welds. Add to that the 20 or so that hold the transmission tunnel and rear torque box. Still drilling new holes for welding is better than drilling out the old spot welds. I also had to notch the front part for the floor pan to clear the inner frame rail and the torque box.
Finally it’s time to clamp the floor in place. I used about 10 of the butt weld clamps to hold the seam together. and several of the welding clamps to hold the floor pan to the frame rails. I did find one cool trick. The drain holes Ford put in the floor. They are placed to allow you get a clamp in there and hold the floor pan and the rear torque box in place. Ford was thinking when they did that, as it allowed them to get the spot welder in there.
With the floor pan secure, I started by welding some of the spot welds to the floor support and the transmission tunnel brace. Then I started stitch welding the seam along the transmission tunnel. If you don’t know what a stitch weld is, its where you weld about 3/4″ of and inch, and move to another part of the seam, then weld about 3/4″ and move again. This is also a good time to check under the car to make sure you have good weld penetration. You should see the weldable primer burned and some white smoke film rising up the tunnel. The stitch weld helps make sure the part never gets hot in one location, which could cause it to warp. Eventually by moving around you will have all the welding done, and all the stitches tied together as shown in the last couple of photos. With the floor pan installed It was time to install the seat riser.
Like the floor pans, no one makes a seat riser for 69-70 convertibles. The 1968 one is claimed to fit, but it does not look even remotely close to the 69-70 style. For 69-70 the convertible seat riser basically looks like the one for the coupe/fastback, it’s just narrower to allow for the inner frame rail. So I figured I could modify the coupe/fastback ones to fit. As you can see from the pictures it was not super hard. I did wind up reusing part pf the original seat riser to make the fit between the seat and the frame rails match up. I cut about 6″ off the outer edge of the old seat. Lucky for me that was not the rusted out part on my old seats. I then trimmed the edge back on the new seat riser as shown in the photo seat riser modified.
This assemble was test fitted back in the car, and clamped in the position that provided a good fit. I then tack welded it in place, and double checked the fit. Once all was good, I welded it up on both sides. Given the overlap and welding this part is stronger than the other. As you can see in the last photos, it looks great, and would be very hard to spot. Much cleaner than using the 68 part, which would stand out.