From what I remember 4130 chromoly, yfz 450 front suspension, full floater and no-link style rear suspension and they were working on a wicked grand prix style rear suspension,any motor, They were quite a bit lighter and stronger than a stock 250 chassis.  IceRacer(carl) is the guy on here to ask about them, he designed them and I believe is putting one together right now. They can also take your stock frame and put a yfz front clip on it.