The two style heads are different in that one won't bolt up to the others block. You can run the same exhaust setup on either though. That part is pretty much the same.
I ran into some trouble when I swapped my 87 305 for an 84 305 out of a Camaro. Very few parts were interchangeable, however the exhaust were.
I went the opposite direction and installed the cheap Dynomax header/dual exhaust kit from Summit. I could actually tell a difference in the power. Plenty more with headers. It may have been because the Cat was pretty clogged too though.
Any engine would run better if you give that hot air somewhere to go.