Hi Jake,
It sounds like an over rated golf cart motor. Got a picture of it?
I think all D&D motors are 6.7 inch diameter. Even their biggest model at higher voltage is often marginal for a car at high speed. Spend some time looking around the site here, in the "garage" and the EValbum. Even use the search function at the top of the page. I think you'll find most use a larger motor and higher voltage.
major