Basically the 350, 327, (331 is an overbored 327) and 302Chevy, were all the same 4" bore block. Size was determined by factory crankshaft stroke, 3, 3.25, or 3.48. If I remember right, the Hemis were destroked with a custom crank that was probably available from Direct Connection (so it would be nhra legal) to 366 0r 398 inches. The E-bodies were difficult to get down to weight, so they started running Colts. Evil little things with that much power.