I have an MTD lawn tractor in need of a new engine. It seems that I cannot get the same model# for replacement. Can anyone tell me what other engines might be a direct replacement for mine? My current engine is a Briggs & Stratton Md. 42A707, Type 1550 01, Code 9510315B. 18 HP Powerbuilt, twin cylinder, cast iron sleeve, verticle shaft. I would appreciate any help. I cannot seem to find anyone who knows and I think there must be some other engine that will fit.