You're better off buying a true GT.
My lhs also sells them for only $350
The chassis is slightly different, Gt has a 2-speed (spendy), 2-speed clutch bell, different body mounts, shock towers, shocks and springs, big foam front bumper, and maybe a few other items.
Plus a new body (around $100 pre-paibted), since you wont have one on a buggy.
Plus all the time and effort to convert it!
Losi 8ight OS TG .21
Losi 8ight T Werks Teamline B3 .21
Kyosho 12th scale SPADA Sirio 09
Kyosho Inferno GT RB C5 .21