It depends!
On a bone stock 390 the c7ae-a are just fine, especially if they are re-done and free it would make sense to run them.
Even if you added an alum intake and carb, these heads still wouldn't hurt it. If you added a cam and headers too, then the heads would be the limiting factor, but then there's a whole range of castings or new alum heads to get or re-work.
So it depends on the car/engine/etc - can you describe?
