My take on the whole thing is that it takes basically a certain amount of horsepower to trap at a certain MPH, at a given weight. Even the old mopar engine bible had recommendations about what kind of horsepower it would take to run a certain MPH. The issue I have noticed, is that sometimes guys have engines built where they were "told" what it made on the dyno, but they run it at the track and it doesn't even come close to the MPH number it should. There natural reaction is that "calculators" are all wrong........ BUT I can tell you for sure, a REAL 500 flywheel horsepower in a 3200 LB car, will trap at somewhere around 120-125 in the 1/4 mile.
