Quadrejet, Quadrejet or Quadrajet. Your choice.
Find a mid 70 vintage carb as the design is better that the 60s version. Keep the dual plane Performer intake as it will give you better low-end response than a single plane design. You may need a Quadrajet adapter for the top of the intake to match the small primaries and large secondarys of the Q-Jet. If you are truly converting to Ramair, I assume you will install a Ramair grind (or similar) cam and RA exhaust headers. Ram Air Restorations makes the best re-manufactured exhaust headers.
Beware of the term “rebuilt” when it comes to carburetors. Very few re-builts you buy over the counter are done correctly. Buy Cliff Ruggles book “How to Rebuild and Modify Rochester Quadrajet Carburetors” and if you are handy with tools and have patience, you can rebuild it yourself. Q-Jets must be set up to match the rest of your engine or they won’t work correctly.
I say all this because I have set up my 68 the same way. The engine was re-built by Jim Lehart of Central Virginia Machine service. My cam is a Comp Cams XE274. Here is a video of the first at-home fire up of my engine.
First Time Fire-up of the 68 GTO 400 - YouTube