I'm gonna go out on a limb here cause I'm bored and waiting for answers myself.....
Ok, back in high school, I was big in to RC. Had bunch of radio,and remote controlled toys. I had this HUGE remote controlled truck, but walking behind it everywhere sucked. So I had the same idea as you have now. I decided I was gonna make my own gas powered rc car out of this truck, a broken Tamaya Grasshopper,and some small diameter copper tubing. I drew out my frame design, then started to cut tubes to make the frame. My dad showed me how to solder copper, and I got to work... I made a frame like a sand rail, tube chassis,big enough for the truck body to fit. My dad put some small plates where stuff would get screwed to, I think he riveted them. We mounted a small weed eater engine. Then I used parts from the grasshopper to make the rear drive and the wheels and tires. My dad got me a long skinny bolt to use as axle. I used a gear from the gearbox as the axle sprocket and my dad put one on the engine (I don't remember how) . We used a big thick rubber band, from his work , as the "chain". This all worked great as well as the swingarm. I failed big time on the front steering, so fast straight lines where never possible. But at slow to medium speed, it would handle decent and really sling some mud...
The thing I built was light enough that the front steering components and steering servo was good enough for the job. The bigger/heavier it is, the bigger steering servo you will need. The throttle can be done with a cheap walmart rc toy servo. But, if you want brakes, get a good one. You can pull for throttle, and push for brake,on a pistol grip controller. That's fairly simple to set up..
I done lost track....... Exactly WHAT do you wanna know? I'm no expert, but I do know a little.....
wait.... You talkin bout ME? 
I pooped a little..... 
