[speedygonzales]

I'm sorry but I have lived with my sorry ass Vortec for 20 years now and I can tell you you won't get there from here.
Vortec 5.7 in that year were rated at 255HP. You will not get to 400 with that engine unless you either change the internals AND use a port fuel injected intake such as the RamJet intake (which is Vortec bolt pattern). OR you put some sort of power adder like a blower or turbo charger on it. The fuel/intake system standard on those engines tops out near 400HP and are riddled with problems. Let's not forget the fuel delivery would need to be stepped up as well which is not easy on a Vortec setup.

However, the internals, having several thousand miles on them, will not hold up to that if they aren't changed. If you're thinking of changing a cam in old engine, forget that too.

If you want to get to your goal (not sure why you'd want to in a truck) then your best way to get there would be a crate engine. Now depending on how you intend to register it AND your state's inspection standards, it's possible that might not work. Obviously if your state doesn't do inspections, you're good to go.

An example of why that won't work is here in VA we have state inspections. If any SES lights are on OR don't work, you fail inspection. If the engine is swapped out, the PCM probably WON'T work with the new engine. Therefore the PCM will set a SES light. If we register a vehicle as antique (25 years old or more) than we don't have to do inspection. However we are not supposed to use a "antique tagged" vehicle for daily use.

Also keep in mind that most trucks of that year came with a 4L60E and that unit is good for +- 300HP tops. That would also have to be addressed.