The correct gearhead motor needs to be selected as Panther G pointed out. The link he provided shows rpm and I believe that is probably an unloaded speed. Didn't do a deep dive into the site but what you really need is a torque speed curve. Torque is what you are after ad for a given motor size you can only fit so many gears into so much space.
Not saying youshouldn't investigate further but these things have been around for years and years and if it were that easy I imagine Tamy or HL or whoever would just put these in instead of making all the space for their own custom gearbox designs.

Perry