Add 273's, 340's & 360's to the "318 Race" ?

Plus the system assume you took full advantage of your mods. If you buy a set of performance heads but build a 375 hp engine with 550 hp heads. That can't be accounted for unless everyone is willing to chassis dyno test their car.
A perfect example is the 318 car I entered last year. I had to subtract .4 for the worked 318 heads. I home ported them with a dremel so they are worked. But, I could have cut them .040, and installed larger valves and got the same penalty but dropped the E.T., and maybe enough for the win. That's why I said earlier, J par's car took all the hits in the box, but didn't fully take advantage of any.. LOL.