Have you ever obtained any numbers on the straight-leg booster carbs, like the common 3310 750's? If so, what have you found regarding their actual versus advertised CFM?
The straight leg boosters are about a 40cfm handicap, compared to the down-versions.
I did a 650 DP (4777) Holley for an iron head 360 I did a few years back..
That carb flowed 709 as shipped from Holley, with the choke door removed.
When I added the AEM Down-Leg Stepped boosters, it immediately shot to nearly 750cfm, after thinning the shafts, flow increased to 792cfm. That was one crisp carb!
I'm going to be doing another one of those sometime soon, so stay tuned for that.