Can you tell us a bit more about it Mike? Is it OHV or side valve? Can you give us the string of numbers from the air cowl? Is it an I/C (Industrial/Commercial) engine? The I/C has cast iron cylinder liners, the light duty engines usually have an aluminium bore.
One issue is the way the engine is packaged: it may be quite a job to get it to fit the body work if it has a muffler where the steering is supposed to go, or the cylinder heads reach through the bonnet. It also needs to have the same diameter and length of output shaft.
If you provide details of the engine, we can try to estimate whether it will do the job of the original engine, but whether it will fit requires access to the mower, and photos or drawings of the engine. You will have to do that part yourself I think.
