Depends on if it's for a 2 or 4 stroke engine. Do you have a model number plate on the deck?

If 2-cycle, your best bet is to find another LB with a 'Duraforce', like a 10323 (usually found cheap) and use the engine and parts from it. If its an older deck, it came with the 'F' engine. There is no difference in any of the LB 2-cycles from homeowner to commercial - they all are 'commercial grade'. Even a 'V' probably would work, but ut's a 4.5 HP engine (as were the earlier commercials. The 'V' came on '90s 10201, 10301, etc.