Even though you want a self build buggy, I think the RTRs suggested above are your only option unless you can spend more. The OFNA RTRs can't be beat. They are durabale and raceable. If you look at the AMain site, check out the GS Storm Evo. I've got the older Storm and have had for 4 or 5 yrs and it's still running strong. This new one is even tougher, awesome engine, powerful and easy to tune, and parts are cheap. Only your local hobby shops may not carry them, which means ordering replacement parts from A Main. But like I said it's tough. The OFNAs are more common though, I have to admit.