Why? They're all the same from 68 to 76 when they went to the cast crank and even then, other than that, they were very similar. Although I would try to stay with the forged crank engine, simply because the block, crank and rods are all different on the cast crank engines. You're just making things difficult on yourself which makes ZERO sense since the car no longer has the original engine. So even finding a 71 engine and transmission is a moot point since it won't be the original.