My buddy said to try dropping down a tooth on the top gear, only problem is that the alternate top gears have been discontinued. I need an 11 tooth top gear. Now the 1981 300s still have from 11-14 top gears still available and the parts fiche for the chaincase looks identical to the 340 chaincase, but they are a different part number. I'm thinking the number of splines could be different on the jack shaft...but I don't know forsure. Does anybody know if these gears are interchangeable?