Slelflyer, the biggest challenge I faced was the x-frame crossmember. I am putting a 700r4 behind the SBC and the old 3 speed mount was not going to work. I had to cut it completely out and fabricate a new one several inches farther towards the rear. Not a problem just time consuming. The other issue is how the engine mounts at the front. The 60-62 series mount at the front of the engine on a plate riveted to the front crossmember. The later SBC/BBC Engines Mount on the sides of the block. The frames are not drilled for the later mounts and a later mount will not fit the frame. Aftermarket mounts are available and require you to mount everything to the engine then drop it into place. Then mark for drilling the frame and pull the engine back out. Drill your holes and put the aftermarket mounts in place. Now your ready to put the engine back in. Be ready to fabricate lots of stuff. Nothing that can’t be overcome. Just a large PITA.

Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
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USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)