Funny. These days I try not to tell somebody, at say a car show, that they are wrong about what they "know" about their car because in the end they just write me off [censored] an A-hole or somebody that just doesn't know what he's talking about. But I have to agree that something was way off on those Dyno numbers. Unless something was bad wrong with the qjet and something very right with the Holley there should not be that much of a difference. Did the OP say that he built the qjet to Cliff's recipe or that he had Cliff build it? I can't remember what intakes were used but the Holley would've required a spacer to mount on a spread bore intake. Might account for a few ponies. A lot of the time the first pull doesn't read as high as the second or third but usually not that much. I think a fairly well put together 455 with a good carb and good exhaust flow could possibly make 490 on a generous engine Dyno. I could be wrong.