Westfield actually makes a V8 model, called the SEight (play on words, the normal car is the SEi). It's intended for a Rover V8, but I've seen one with a 600 hp SBC in it. LS? No, you're not the first to think of it 
I think finding the transmission might be the tough part. The T56 won't fit that well in a Seven, but a built T5 might do the job.
Notice the intake on that Stalker? It's been turned around. Nice trick that for getting the engine underhood. Also, there's absolutely no bracing in the horizontal plane in that engine bay. That'll be one noodly chassis.
I can tell you that on our local track, the 250-ish hp Westfield is faster than my 148 rwhp car. But only by 0.3 seconds, and it's on better tires too. It's not all about power.
Square left in 50 caution ocean!