I have not found a single mention of modding a Gen 2+ intake manifold onto Gen 2 heads which sounds like a good idea if someone already had ported Gen 2 heads. And it would be a bolt on.

From what I've found searching, the Gen 2 manifold bolt holes are staggered whereas the subsequent Gens are not. But it looks like the gasket surface angle may be different from photographs. Ports are evenly spaced so if block bore centers unchanged, port spacing could be the same.

And am I right that the Gen 5 plenum has a bolted on cover???

Each generation appears to have a completely rethought intake.