Depends upon what you intend to do with the car. If it will be a daily driver car that you mostly cruise around in I'd consider trying it as is. If it isn't up to par, just an intake manifold change would be my next course of action.
I would only upgrade to 4V heads if I wanted to drag race the car, or drive it very aggressively. 4V heads like 3.89 gears, manual transmissions, and headers-without all three I would stick to the heads you have.
4V iron heads, by the time you build them properly cost almost as much as aluminum ones ready to go. With any head change, you will need a top end gasket set and will need to verify proper pushrod length and valvetrain geometry-most likely you will want to add roller rocker arms, guide plates and hardened pushrods.
Aluminum offer the advantage of lighter weight and slightly improved detonation resistance, but I prefer iron for the durability and the fact that they seem less prone to head gasket failures, as the expansion rate matches that of the block better than aluminum.
