Do not get a HK/turnigy/cheapo motor. It might get you the speed you're looking for, but it will overheat and/or fail very quickly in almost vehicle (especially one as heavy as yours). You simply can't cheap out on the motor. Those cheap motors are very inefficient and will heat up like none other even if it didn't fail immediately because of the quality.
I really wish there was an efficient and very low-cost motor, but there is no such thing.
An L-size Feiago would be a step up in quality, efficiency, and price. You might be able to limp around with one of those.
Really, $160-170 for "Buggy size" 1512 Tekin or mamba motor would be a very solid set-up.
If you really can't shell out the dough, maybe a used 60mm medusa or just a Feigao.