MMP will handle 1/8 but not for speed runs! If you want more than 75mph on a 1/8 scale MMP won't handle it. You can try a Xerun 150 amp if low on budget.
what about the hardcore onroad cars like the MRX-4/5 / Serpent 966 etc? I thought these (and I was planning on converting one) would be the way to go for handling / speed.