Ask the question on ebay or find an old Merc dealer who probably has a lot of "parts" engines lying around or better yet has guys gut oldies for their usable parts and has then shelved and inventoried. Both are 2:1 ratio but as Fazt said, totally different lower units and the shims are important....need to get the right amount and that takes a gyzmo gauge you have to stick in the rear of the LU gearbox to measure the clearance between the F gear and the the drive shaft pinion.
