Can you locate a model number? There should be plate on the rear bumper that lists it or it may actually be written on the body. The two most popular versions are the TR-351 and TR-381, but there are a couple other models as well. If you can figure out the model, I can tell you what engine it oringally came with.
Also- does it have rear suspension? This will also help with model identification.
Post some pics if you can!