Track doesnt lie, but HP calculators can't take everything into account either...
For example... 37" tires on 24" wheels and 4.56 gears, compared to 32" tires, 16.5" steel wheels and 3.73 gears....
You can't tell me your 556 HP holds true in either of those configs? That you'd run the same time and trap the same? My truck runs consistent 12.6's and 12.7s here - and it's a dually at 8000 pounds... different HP calcuators produce different results for that, just like different dynos give me different #s with exact same tune... Lots of things don't go into an HP calculator - just the nature of the beast! They'd be too complicated to use otherwise. I very much agree power is proven at the race track though. More by trap speed than anything else. ETs have way too much depending on them, where as trap speeds are generally real consistent with a semi-consistent run.
That being said, Nick's point is my point as well in comparing dyno sheets. Unless it's same day, same dyno - comparing sheets is like comparing apples and oranges and determining they're the same.
All this talk about the track really has me itching.... I wish the snow and cold would stop so we could get on with a nice warm spring!!!