ATV Racing can do anything you want. The LT kit on the pilot is the way to go for any serious jumping or riding in whoops. The can also add about any sled motor you want to the chassis. It wont be cheap, but it will be fast. You can try the conversions yourself, but unless you are an experienced fabricator you will run into more headaches than you can deal with. If I'm not mistaken Dennis' car was one that ATVR did for a guy, but he either ran out of funds, or just decided that it wasn't for him, and he ended up selling the pilot to Dennis with issues still to be resolved.
No matter what you do you would probably be better off looking for a used long travel pilot versus the cost of a pilot plus the long travel kit installed. I have seen long travel pilot go for as little as 7500 and as much as 16000. All depending on the condition, other upgrades, and current owner's knowledge of the prices they are bringing.
A full on modified pilot from ATVRacing is gonna run you close to 15K not including the cost of the stock pilot. From what I understand they now make a sweet single seat car that will shame a pilot, and I'm pretty sure the price tag on it is around 15-20K depending on options.
Another option is a drakart. They seem to be selling well, but supply of parts and dependability seem to be major issues with them. They start out at about 18K and go up from there, but used ones can be found for 10-15K. The drakart website is
www.drakart.com