well yeah I'm not saying necessarily that all stock f-bodies had 300 fwhp, the single cat cars definitely had a restriction there, however there is overwhelmingly evidence that the hp ratings were underrated similar to the ls1. saying that the fwhp is 275 because that was the advertised number is bogus.

 

Definately underated. My understanding is that rating is typically off by 25-30 hp. For the guy who uses the mustang dyno it is a known fact that they dyno lower than dynojet dyno's.

 

i dynoed 257 320 with bad manifold gaskets, a flowmaster catback, and 4.10's through a slipping clutch when he punched it.