I'm looking for an 800 CFM Quadrajet for my 455. I'm looking to send it off to TA to be completely rebuilt, so it doesn't have to be working now, just needs to be complete. I'm not sure if there is a particular year that I would need, but it will be going on a 71 motor with a 70 intake.
'71-'73 are probably the best. At some point after that, the pollution controls get worse. I'll check to see what I've got. '70's are 750.
I believe 71 carbs are (750) too..but I'm no genius-check this out for more info- don't know how accurate it is- http://buickperformance.com/qjet.html