True horsepower?

ok well if Moroso says 285hp for my on track hp, and factory stock is 275 or as some say its underrated, that don't say much for my add-ons/tuning:(
but if you go by wallace@302hp its more in-line perhaps. Basically then if you put the same 8x26" slicks 3.55 geared bone stock 727/340 '70/'71 Cuda it would run 13.3's from the factory?