C4's are the better bet and yep they are lowrisers. The C8's are the later velocity port design close to the MR. I would also depend on your exhaust mainfold or header choice. C4's have the vertical 8 bolt pattern and the C8's can have 12,14 or 16 bolt pattern. It's also wise to price out all your options. See how much it'll cost you to do the C4 heads and compare that to a new set of Edelbrocks. Those are in the $1300 range new out of the box. Sometimes the prices are close to each other if a shop does all the work. If your handy and can do your own porting and rebuild your ahead of the game with the C4's. Just have the shop do the machine work.

G.