A formula
Here is a formula that you may want to take to whoever set the budget up for this wild scheme.
R/C + Cheap = Crash = danger
$15 wouldn't even buy a wheel for a car like that.
A decent (safe) R/C car for that size engine can easily go for 800 bucks. They are NOT toys. All of these models are actually minitures of the full size. They must have a 'certain' amount spent on them to assure they are safe. There is also alot to consider when using a gas engine...IGN noise, the parts connected to the engine must be able to withstand the added power, suspension must be able to withstand the added weight and forces etc... A gas r/c car is a high power machine, and when they get going they can really hurt somebody is care is not taken. I have seen small cars (.21 glow engined) that will go near 80 MPH!!! I would seriously recommend they rethink they're budget or rethink attempting this.