I hate to keep syaing this, esp. when the question is qaudrajet vs. new quadrajet, but I have an Edelbrock Performer 600 and it does not mine any angles I give it.
Even the steepest hillclimb that I can find is absolutely no problem, not even a hiccup.
How steep? I don't have an angle finder or whatever, but steep enough that if you stop forward momentum, you're going down and it won't be pretty (hope you have a rollcage.)
Stock out of the box, not even those offraod floats they sell.
A friend, however, has a Holley 600 and it's crap for offroad (at least his is.) Hiccup over over anything, and don;t even bother try to climb anything it will stall out.
Just my $0.02
-- Mike
Oh, about the Quadrajet. If you were to buy one, I would go with the the new Edelbrock one. I personally think they are hard to tune, but I tried to tune a clapped out one so I'm sure a new one can run flat out. I just got tired of all the little pieces!