I'm looking to change out the old tired 305 out of the 81 for a built 350. The 305 is out of a 1979 Chevrolet Caprice. The 350 is out of a 1967-1972 Chevrolet car (not sure the model, but that's the casting # info). Will the motor mount brakets line up right? I'm hoping to just drop it in and bolt it up.

ya it should just drop in without any probs goood luck

I believe the block size is the same. 305 has smaller heads and crank and such. So it should drop right in. you may have to change motor mounts though