[BVR421]

quote
"I don't think I need a 800/850 cfm Qjet for this mild combo...."

that is true but the later 800s will be a much better fit on the late manifolds. choke heat, throttle linkage, etc
keep in mind the qjets secondary air valve only opens as far as engine manifold vacuum opens them in spite of the actual secondary bore plates being wide open. this makes the qjet self regulating as far as cfm. that along with the very small primary bores makes the qjet very fuel thrifty whether accellerating or just cruising. It is actually demand based self regulating as far as actual cfm. It feeds only the amount of air and consequently fuel, that the engine actually can use at a given speed and load. The factory used a 800 on the 455SD motor as well as the puny 301. Basically the same carb although each with appropriate calibration. It worked fine for both.