Q-Jet, bar none. I grabbed lots of different metering rods and hangers when I was bracket racing, so there out there and easy to find the tuning parts you might need.
If the Q-Jet is from another 350; no mods will be necessary, just adjust your air door spring tension to suit your altitude.
People will give Q-Jets away because they HAVE to have a Holley or Carter AFB (Both would work, but are junk,IMHO), so picking up extra parts is a cinch.
Stay away from the 800 cfm model (it has the larger primaries). Those are for large displacement torque motors and will be too rich for a 350 sbc.
The #2101 manifold will work, or an aluminum manifold from a mid-'70's sbc will work; just block off the EGR port. The Q-Jet will bolt right up with no adapters.
Carb adapters rob your CFM, so avoid them if at all possible
