I'm kinda on the other side of this a bit on a couple of things - just one guy's perspective and experience.
IMHO, if it's got an auto...I use vacuum secondaries, period. And overall I'll pick vacuum over mechanical for anything that's mostly street unless the engine is really hot...making over about 1-1/2 hp per cube.
for a bbc, there's enough flow that a square-bore carb can be a bit bigger than the math would indicate without bogging intake velocity - the primaries get a good demand signal and it works ok. IMHO the 3310 is a good "utility infielder" carb and works well for a bbc if it's tuned right. Not disagreeing that smaller carb will work just fine, and the street avenger is a great pick for a put it on and go carb.
I run a 3310 on my c10 355 making 375 hp and I've swapped in and tuned a few other carbs over the years and never found a bit of difference in throttle response or power...but I did find a very slight fuel economy benefit with a 600 vacuum secondary carb.
I did learn to hate edelbock performer carbs, though
