need more power

[fair1138]

I picked my truck up in 2006. I’ve done a lot of working getting things right, and it runs good. But being a typical guy, good is never enough. I need some advice what I can do to make some power. I didn’t build the engine, but I’ve done a lot of external work and research on it. It’s a 454 #3999289, LS6 heads #3994026, gear drive, roller rockers 800CFM Holley Carb; jets are 71/75 and Trick Flow ceramic headers 1 7/8” that flow into Flow Master 40; 2 ½ outlet. All this connects to a Turbo 350.
Some time ago I took it to the track and it ran min 13’s. Now if I did my math right and guessing the truck weights 4000lbs, that’s maybe 340hp. Seems awful low to me. I have no idea what cam or pistons I have. I wanna do some work this winter on it, but looking for advice on what I should do. Iam married, which means I have a budget…lol. I'll post any pic you need also...thanks