My recommendation would be to purchase a Sportwerks Turmoil. I am not sure if you can get it RTR with radio for $400 but for the money I would say it is the best RTR out there.
Look at the screws and parts on the OFNA. We don't see many OFNA Ravengers at the track but you will see many Mayhems and Turmoils in the 1/8th Sportsmen class.