"Thinking about a 350 and 700R4 in the '53."
On my 1958 Chevy 3800 I used the original V8 front mounts with a manual transmission and the bell housing setting on the cross member rear mounts.
1958?
hmm, in 1953, there were no original V8 motor mount locations?
Also, Chad M, you probably know that 1953 GMC vs Chevrolet-truck from motor mount locations are different (if an adapter is available for '53 Chevrolet)?