Originally Posted by 55 Tony
Don't know if I'll end up with a 4 hole spacer or an open one.
Dual-plane manifold, use a 4-hole spacer. Single-plane manifold, use an open spacer, but don't be surprised if someone from Burnt Stump, Arkansas chimes in and tells us that he made more power with a dual-plane intake using an open spacer. Spacers are not an exact science.