Big block motor mounts??

["67"StepSide]

I have a question about big block motor mounts for my 67. I see that a lot of people on here say that if they're selling big block motor mounts, they are for 67 to 71, and that 72 is all by itself. Can somebody please explain to me why this is, because I'm putting in a front suspension from a 72 3/4 ton under my 67 frame. What motor mounts for a big block do I use? This truck is two wheel drive. Because I'm looking for a set of mounts for a big block, I just don't know which ones I need. Thanks, John