you go with the stock a-body big block k-frame then you need to find the correct block with the bosses so you can use the funky mount they originally used. plus those parts are usually expensive.
Friend of mine bought a 72 440 for his M-Code 69 Cuda. The 440 had the correct location bosses on the block but not drilled or threaded. My friend set up his motor mount and then carefulled drilled and tapped the holes for the other part of the mount. Everything fit perfectly and he's still driving (ocassionally) it with that motor and his original motor mount.
