What servos, reciever, and stamoing are on the motor?
It seems all the above, besides the HPI (no offense) seem likely. They all have the same bumper style, the top plate are the same shape with the on/off switch in the same spot. Exhaust seem Kyosho to me. The belts all run the same path, same...
Welcome to the site. I would do parts sooner then later as they are drying until no longer.
This may help you some.
https://www.rcscrapyard.net/cen-gx1-gp.htm
https://www.ebay.com/sch/i.html?_nkw=cen+gx1&_trksid=p2332490.m4084.l1313