Heads and cam...

I'm not trying to be negative here, but a lot of factors play into what a car would produce horsepower wise at the rear wheels. For instance what size cam are you using, whats the lift, whats the duration? Second, is there an after market exhaust being installed? All that extra air and fuel have to go somewhere. Third, a stock bottom end motor has been rated to around 450hp or so. New injectors, tuning, and fuel management need to be modified as well. The stock 3valve heads have been rated pretty good for air flow and high horsepower has been reported using only a super or turbo charged motor. There have been some recent threads regarding cam and head discussions.

There are a lot of factors, but assuming the heads are ported by a good and knowledgeable porter and quality cams of a good grind are installed, add to that all the bolt-ons including long tube headers and you should be pushing 385 depending on the dyno. People I have seen with ported heads and bolt-ons are normally in the 350 range.
Dan