Tranny cases can be found quite frequently on the different auction sites or with dealers, it doesn't seems to be a big shortage in general. New gearbox cases and gears can be purchased from our club member Mark Lesek. He even makes gears with a different ratio in second gear.
The slider second gear is 1 cog taller that makes the second gear closer to the third gear. Same gearing as the later Chief with slider 14-19 and cluster 22-17-14 where Scout has slider 14-18 and cluster 22-18-14. However as of yet he is not making the sprocket gear, the 3rd gear that the chain sprocket is fastened on. I don't know if he is making sprockets.
mark@dynamicwelding.com
Early Chief (and probably 3 speed Powerplus) has the exact same 14-18 slider gear as Scout and is interchangable. However the cluster or third gear in not interchangable between Chief and Scout. I am almost sure 3rd gear is the same for Scout and 3 sp. Powerplus.
The countershaft bushings, I recommend to have both but at least the inner one (right hand side) changed for a new, and the hole line honed to the proper shaft centerline distance from main shaft center.
The inner bushing is subjected to great forces and sometimes/mostly worn (pounded oval) so the countershaft is loose or not in line with the mainshaft. The bushing can also be pounded in its seat so it is sitting loose in the gearcase. All that makes the gear noisy and accelerate wear. A culprit to the wear can be a worn ball bearing at the final gear, there is a lot of tug, jerk and rattle going on there with the chain.
A telltale that the countershaft is rattling in the bushing can be seen sometimes that oil is seeping out of the gearbox case hole at the end of the countershaft. A proper fit of the shaft in the bushing is zero play, light knock in fit or at worst fairly tight slide fit. Slide fit is really not tight enough. But not so hard that you pull the bushing at disassembly.
If you have the opportunity before assembly to drill and thread the countershaft end at the clutch side for a retracting puller, it makes it vastly easier to remove the shaft the next time.