1/10 scale nitro stadium trucks are damn near extinct. i only know of 2 and neither one is a kit. pretty sure traxxas still makes the POS nitro rustler, and HPI has the nitro firestorm.
nitro off road kits, the only thing i know of are race oriented 1/8 buggies and truggies. and there a bit pricey.
the industry has totally shafted actual hobbyists over the last 15 years. so RTR is really the only way to get going these days, unless you've got deep pockets and want a race car.