missed this
Some examples outside what is said above.
One way to stop wheelies in some MT's like the Stampede 4X4 is put in a center differential. Put one in my stampede to turn it more into a 4wd 1/10th scale Truggy, and it stopped it from wheeling as once the front wheels break traction it unloads the power from the rear, The diff fluid greatly affects this with this setup, (this stampede started life as a Slash 4X4)
Now something like a 2wd Stampede good luck getting that to not wheelie as the majority of the weight is in the rear.
Basically it all depends on the RC you could try wheelie bars, adjusting the shocks like I removed the pre-loads off my Savage X's shocks which made it harder to wheelie. My flux forget that thing it was able to do backflips only way to stop it from flipping was to make a wheelie bar for it. Rc's with higher center's of gravity will wheelie easier(and tend to like to flip in turns)
Maybe look at a Truggy those can still pull wheelies, but generally they are harder to pull it on.