While switching to Edelbrock aluminum heads I was planning on using an F4b intake and selling my performer RPM to gain a little bit of hood clearance. Before I made the swap I figured I would take some measurements. The way I took the measurements was I set both of the intakes upside down on the carb flange and measured the lifter valley sealing area. The RPM intake was about 1/16th of an inch lower in the front and about 1/8th of an inch higher in the back; this gives the carb slightly more forward tilt. There is very little difference in clearance so I Installed the RPM. (And sell the F4B)
I took pictures I will post them tonight if I can figure out how.