Putting a Big Block in a 68 C30 - Question

[Troy.Blackburn]

After 22 years I've just rejoined the ranks of owners of 67-72 Chevy Trucks. My first vehicle which I bought in High School was a 68 Shortbed Stepside 6 cyl 3 on the tree C10. I was the second owner and I had it for 10 years before it was stolen.

I just bought a 68 Stepside 6 cyl with a 4 spd (w granny low) C30. Of course it's a long bed because they didn't make shortbed C30's.

I opted to buy a C30 this time because I wanted the heavier duty frame, but I'm going to shorten the frame to make it a shortbed.

I'd also like to put a big block in it to beef up it's towing capability. My question is should I try to limit myself to any certain year range of big blocks to keep installation as simple as possible? What's the newest I should consider and be able install it without having to change much more that motor mounts and I'm guessing the bell housing.

Thanks
Troy