Yup, Rampage chassis. Fun truck. Has some Duratrax upgrades, including the slide carb on there. You wouldn't want to part with those shocks, would you?
Most likely the engine is tired. No biggie. They are good engines, and should be rebuilt. I usually put in a new pin, piston/ sleeve set, rod, gasket set/ o-rings, head shim and plug. I would also get a Duratrax stage 1 blue head for it (they still make them). Much better then the gray stock one, and was a common hop-up at the time.
In the engine manufacturer part of this forum, there is a guy named Bax that answers the questions about the O.S. engines. Send him a message about getting a copy of the manual for the engine.