Looking for a complete 670cfm Holley Street Avenger Carb

 

I think most 455 ci engines had 750 cfm carbs why do you want less? I am assuming this question by the user name.

 

My username is 455 because 350 was taken, haha. I think most Qjets were 750, I've seen cars go a tenth or so quicker with a slightly smaller, more modern carb. I think it's better for torque off the line, also slightly better for mileage. Not that any of us have our cars for great gas mileage, but if I can get 9 or 10 mpg city instead of 7 or 8, that's a step forward

 

I would imagine you are going to get worse mileage by going to a square bore Holley. The advantage of a Quadrajet is the small primaries compared to the huge secondaries. If you keep your foot out of it you will see an improvement in mpg.