it would be an easy swap, as long as both engines are of similar year. If both are carburated, externally, they are identical, so it should be a very simple swap. The only possible snag I know of is the flywheel and harmonic balancers. The 305's normally use a 7" balancer, which is not compatable with 350's. Some 305's had a 12" flywheel, most 350's use a larger one (13.84" I believe). Other than those two issues, it should be a painless swap.