Ivan,
Did you see this? "I know the sound the carb makes when the secondary air valves open up on the 350 but I didn't hear it anything like it on the short drive I made to test it."
The AFB's I've seen were not square bore, but spread bore carbs just like the Q-jet. If you have room - go for the Q-jet as you seem to want to do that. They are good carbs. A bit tough to find parts for and a PITA to work though.
Good luck,
Jim
