Picked this up yesterday...

adriver said

I'm guessing drums and small bolt pattern.
So you must be contemplating something else besides what you mentioned.

Click to expand...

Two options.
Opt. #1: Pull the drive train, and replace it with the 390, 727, 8-3/4.
Opt. #2: Stay with the slant, and 904 ( beef both up a little). swap the 8-3/4 in, and redo the slant with Centrifugal supercharger, fuel injection.