while I had both frames side by side I compared the differences between a 62 ('90) frame and a late-model ('86) 60 frame. Aside from the obvious differences such as transmission and engine brackets (though the engine brackets were close) there were only two others that I found. One was the rear-most cross-members. The 60 has just one piece of channel connect the rails, where the 62 has two welded together to form sort of an "X".
'86 FJ60:
'90 FJ62:
The other difference was with the round cross-member at the upper mounts for the rear shocks. The 60's is straight with respect to the north-south (front-to-back) axis, where the 62 has a slight forward offset of the right mount.
'86 FJ60:
'90 FJ62:
Otherwise, the frames appeared to be identical. What's also interesting, is that my original '86 HJ60 frame has the same cross-member designs as the FJ62.
I spent the rest of the afternoon removing hardware and cleaning the "new" (62) frame the best I could which was an immensely tedious process with degreaser and small hand brush. I finished at dark and slid the 62 frame into place.
Before:
After:
