I've attached a pic of the motor I'm building along with the HP & Torque curve I should have with this set up.

It's a bluprint 355 short block with an edelbrock top end kit #2098 (heads, cam & lifters, intake) and a holley 770 street avenger.

My question is what will a 1/2" spacer do for me? I've read many articles and half of them say a spacer will improve performance while just as many said the spacer did not make a noticable difference. The intake is the rpm air gap so it's pretty tall which is why I wonder if a spacer will make much difference. I realize that I'd have to get it on a dyno to be sure but am asking for technical opinions from the experts! Thanks.

Basically, the "open" style spacers are supposed to give more high rpm power, where as a 4-hole spacer is supposed to give better low-end torque. And a phenolic (composite) spacer helps to isolate heat from the manifold to the carb. Your air-gap manifold is designed to isolate heat to the carb anyway, and is raised higher than a normal "low-rise" manifold. So, I would try without a spacer. I doubt you'll notice much gain unless you're crunching numbers at the strip.

Thanks very much. Glad to hear it wouldn't make a big difference as I already have minimal clearance.

Thanks again.