Next problem... 338 hp out of a 427 bbc and 6-71 blower? Have you checked to see if there are any rotors in that blower case? LOL...
Is this a bone stock engine with a old detroit 6-71? Fuel injection is not going to work unless you have a good high air flowing set up. Most mild sbc are capable of a easy 600hp with a 6-71 and pump gas.
Im not trying to be a pickle but we have some base stuff to get right first.
Tell us your specs of all ur parts please