I don't have an 1/8 on road, but will give your thread a bump by asking where you plan on running that thing? I wanted 1/8 scale bad, but the only place I found to run them is in Cincinnati, and I live in the Columbus area.
I own a mrx-3 I'm running futaba digital 9450 for steering and 9351 for throttle they seem to work pretty good fast and responsive I'm also running a sirio sp21prpro motor it runs good we dont actually race them yet only three people have them and we dont have a track we play around on a big black top parking lot what motor are you going to run?