As far as race gas goes VP C16 is a middle weight fuel with respect to specific gravity. What that means is that it can support a bit more HP than comparable pump gas especially pump gas that has 10% ethanol (most premium fuels). Also that 624 number I am sure is a max effort. That is just way high. I know that he modifies the walbro pumps to work better at higher pressures, but still that is a very high number. It is not the average, just so you know.
Still 710>624 and 690>624 so something is NOT right with that J&S dyno.