Holley Street Avenger on 408 / 416

I have an aluminum 570 version slated for my built slanty,hope that's not what
I'll be dealing with,not that it won't be cured.I just have better things to do than chase
away driveability issues outside normal adjustments/changes.
My only experience w/one was a customer w/a chevy 350,comp cams,world prod.
heads etc. he had stumble/flat spot, then over rich on the top end. The float levels out of
the box were way off, pri. side too low, and sec. side too high, after setting them correctly
it ran perfectly,backed up by my wideband FAST A/F setup which also showed the lean cond.
on initial accel. and the rich cond when the sec.s opened(10.8:1 !!).
Hope thats helpful to you, is there anything else that changed when you did the carb
install? Sure no vac. leaks etc.?