just wondering what kind of power will the locost chassie take?

I guess that all depend son what exact chassis you are building, and the thickness of the steel box section, how much strengthening/cross bracing etc you put into it.

I'm wondering about this myself, as I have decided to go for a BMW donor, so whatever beemer I get my hands on (just waiting for one at the right price) will govern how I build the chassis, what steel I buy etc.