Quick question,

What was/is the difference between a 1970 Chevy 350 CI and a 1970 GMC 350 CI?

What parts will swap.

I have a 1970 GMC step-side/fender-side and the engine looks no different than a normal SBC.

They are both GM, but so is Cadilac, Pontiac, Buick & Olds, but their engines are a complete different animal.

TIA,