Sounds pretty close to 350 hp to me. Maybe a tad more with the good compression number. Maybe up to 375. Why not take it to a chassis dyno and stop all the guessing? Didn’t your “professional tuner” have it on the rollers? If he didn’t he should have.
The shop that tuned it for me doesn't have a dyno. They are a resto shop that has a lot of experience installing Snipers. One day I would like to dyno it.
According to Motortrend, the stock 340 made 320hp. That's why I though the mods would be good for about 70 more horses.
