I'm looking into swapping an early model, Carbed 454 engine long block, into a van/truck that came with EFI. The Van/Truck it's going into broke the crankshaft, I'm pretty sure it did, the flywheel turns but dampner doesn't! I want to use the early model block/heads or just the block assembly and put it in the EFI engine. Is there a differance in the blocks? What do I need to swap and can it be done?  

As long as the later model engine isn't a Mark V big block, you can swap short blocks no problem. Easiest way to figure it out, buy a head gasket for hte old motor, a head gasket for the new motor, and see if they're identical. If they match up perfectly you're good to go, if not, then you'll have to swap the whole longblock.