For me, I purchased a RC-10-GT factory team car kit in May of 2003. I assembled it with a many alterations from the get go. For starters I went through the trans added a aluminum diff gear, steel idler, titanium top shaft and removed the slipper clutch assembly. In its place went a 2 speed spur gear set. For the engine, I went with an O.S. RG 21 that I shaved some weight off of, 2-speed clutch bell, HPIs nitro RS4 pads in it and Custom motor mounts that bolt in the existing chassis holes. The exhaust is a custom made for that specific engine, RPM range and dumps out the back of the buggy. I moved the throttle servo forward and to the center of the chassis “where the fuel tank originally went”. I put the battery pack where the throttle servo originally went, to counter the weight of the engine. I went with an OFFNA fuel tank that fits nicely by the steering servo. I went and chanced the rear caster to 2 deg per side, and lessened the caster it the front. Yet, with all the changes it looked like it was bought that way. I currently have run almost a gallon of fuel through it and yes its fast, but what a fun show off toy.