Bobby - I'm using the Performer RPM along with the 600 cfm E'brock carb. It seems to be a nice trade off - dual/single plane. The Performer(idle-5000) vs Performer RPM(1500-6500) - the RPM moves the performance range just a bit higher in the rpm range. I bought mine new at a swap meet for $100, and then had it Jet-Hot coated. Of course the camshaft that you use should have some bearing too.

http://www.edelbrock.com/automotive_...ord/ford.shtml