Do yourself a favor, get an electric.
Tuning engines isn't fun. Tuning clutches isn't fun. Having to do it over and over every time the weather changes certainly isn't fun. Having the kid down the street get an off-the-shelf Traxxas electric for his birthday that will absolutely dust your temperamental nitro is humbling. Not that that matters, since you'll be tuning for his entire first battery.
Brushless + LiPo has nitro beat all the way around. Faster in most instances, no clutches, ridiculous run-time, and no maintaince. If you're really bent on tuning, you can tune many brushless controller with an easy-tune card or a laptop.
If it were me and I was just curb jumping the neighborhood and had $400 to spend, I'd pick up a 1/16 E-Revo VXL, a couple 3S Turnigy LiPos from Hobby King, and an inexpensive balance charger. You'll end up with a 50 MPH, nearly-uncontrollable riot of a truck that you will only need to touch to replace broken parts or install upgrades (which there are many).