The Q-jet, when properly rebuilt and tuned
for the application, is one of the best carbs ever designed and built. Problem is, most have no idea how to properly rebuild them or adjust them. Just replacing gaskets, float, seals, etc. , wont return your q-jet to its proper form.(I also suggest sending it out to a Q-Jet Pro) The q-jet will offer better idle quality, off idle response, full throttle power, and the best possible economy of any factory carb.
There are cars out there knockin down 25mpg, others running 9 sec ET's, others pulling huge loads with big block trucks, all with a Q-Jet. There are only 2 sizes of Q-jet, 750 or 800cfm, yet they can be tuned to work on anything from Chevy and Olds 307's to big torque Buicks and Pontiac. From grocery getters to Super stockers.
My first suggestion would be to pick up Cliff Ruggles Q-Jet book, its current considered the best Q-jet book available. Check Amazon or here:
Cliffs High Performance Quadrajets :: Qjet Carburetor Rebuild Kits, Parts, Quadrajet Rebuilding, Quadrajet Parts, Bushing Kits, Carb Tuning
Read it a couple of times, then decide if you want to tackle the rebuild/mods yourself, or send it to a Q-jet pro.
Good luck with your decision