Hi.

I say the lpr or the o.s motor. The lpr makes insane power at the low end and high end. I think it makes 4.02 hp at low rpms which will get that big truck moving. I head a lot of good come from the o.s motor too. Myself had the same question because I'm wanting to find a better motor than what's in my losi xxl when the time comes. The 454 in the losi is made by lpr if that means anything to you.

Good luck and enjoy wooping up on your kids or the other way around lol.