the bulkhead on the RT is about 2" longer then the normal rev bulkhead... and hte whole chassis is quite a bit heavier. IMO puttin an 800 would be a real pain... and then you just got a bulky 8.
as for the motor, if you cant find a good used one, most likely do what everyone else does and part it out. they are fun sleds but $$ to get back together if they puke.