Anoter helpful point, make sure "you" order the cam and springs together. I let my engine builder supply them and he didnt buy the matched kit like he promised. He built a kit with what he thought would work. After 3 different coil bind failures, I called CompCams and ordered the correct springs and had to pull the heads to machine them as the the springs for that cam are much larger in dia. Ive never had any issues since and it runs like a champ.

Mine dynoed at 402 with heavy rains (high humidity = low hp). So with the injection it was limited by the air intake design of the manifold. It should be good for an easy 10% more with a carb like your demon your talking about. Ive got ported and polished Brodix heads so you might have to add that in to estimate yours accurately, but you should have no problem getting 425-450 horses with the 383.