If you have time this is the best option. I'm no pro by any means, I've had just about every carburetor there is over the years.. Quadrajets, Holley's, Demons, QF, Eddy's, Pro-form, Motorcraft, Marvel Schebler, etc, along with Vacuum and Mechanical secondaries. On my latest build I bought Ebay carbs, rebuilt them, tuned them then tried another until I found what I liked.
I don't necessarily agree with the constant advice on vacuum secondaries or the need for a choke. Heavy cars with the right gearing, a stout motor and a driver that knows that you don't floor it at 1,500 rpm do great with a double pumper, some motors for whatever reason need less choke than others? I had a 750 Demon (no choke) on a stout 400sb, I got so sick of choking that damn thing with my hand I swore I'd never own another chokeless carb! My current motor, I tried 3 carbs before buying a QF and with all of them it would cough and run like total crap until the choke was fully open? I locked the choke wide open and never had another problem. When I settled on the carb I wanted I ordered one without a choke and have never needed it and that's in Ohio.. -0 degrees and it starts?
Testing is an important tool. I tried an 870 Avenger (vacuum sec), 850 Demon (DP), 750 Pro-form (DP) and bought a QF 750 (DP). This is a stroked 400 (456), what I found was both the 870 and 850 worked very well except driving around town, the 750 Proform ran flawlessly everywhere but there was a slightly noticeable difference in the higher rpm's. The QF I bought (choke delete) flows better than a standard 750 so I gain a little of the top end back while running wonderfully around town. 16,000 miles and it never missed a lick, not even a hint of bogging, zero hesitation.
