Will a 1970 Chevy 350 intake manifold fit on 1980 305?

No, a 1970 Chevy 350 intake manifold will not fit on a 1980 305 engine. The intake manifolds for these two engines are different due to the different head designs. The 1970 350 engine has a different head bolt pattern and port configuration than the 1980 305 engine, so the intake manifolds are not interchangeable.