So is it a body swap or a chassis swap? I don't know which it's called, but I'm taking a '67 VW Type 3 Squareback body and putting onto a '90 Miata that I've stretched (to fit the wheelbase) and cut the body off.
With the Miata's wheelbase stretched to match the VW's I started prepping the rest of it for the body/chassis swap. That mostly means cutting everything off the Miata that would intersect with the VW Type 3 Squareback. I used a measuring tape, looked at photo's of another guy who did the same swap, and just guessed.
I'm leaving the inner rockers and will use them if I can, but they will be too tall compared to the VW's. I could chop them to the same height, but I'd rather keep theme for strenght.
The hardest part to cut down to size was the areas under the A pillars. It was a 3d matrix of sheet metal, it was extremely difficult to cut a saw in there. I just had to cut little tiny pieces off at a time. The VW Type 3 will just barely squeeze over the innermost sheet metal, the part that the clutch linkage and fuse box are bolted to on the driver's side and the air blower motor on the passanger's side. But they would not have fit if I was using the Super Beetle. I don't think.
Had to be real careful around the wiring loom! I nicked it just a little bit.
But that created a hole between the interior and exterior, as well as a pretty nasty surface for welding to (this is an important spot for welding the VW body to the Miata). So I made a patchwork of sheet metal pieces to, umm, "repair" it. It was good welding practice! Still too many holes though, but they'll get covered with seam sealler.
Onto the VW Type 3 Squareback...
First order of business was to throw out 99% of the garbage in the interior. Only thing I kept was the stuff on the dashboard, the mirror, the door handles.
The weather was warm just long enough to wash it and experiment with putting a thin layer of lindseed oil over the old faded paint. I tried buffing with compound first but I preferred the brick red/burnt orange color that resulted from the oxidation. I'm really happy with how it turned out! (it didn't look this greasy as in this photo once it cured). Check it out:
If it looks a little greasy in that photo, it's because it was taken just after applying the boiled lindseed oil, and after it dried it gave a real nice satin sheen.
With the exterior cleaned and shined up, I was finally ready to tear it apart.
Nothin' else to do except get the body up off it's old chassis, and drop it onto the Miata chassis!