HD Mainshaft Bearing Thrust Plate, Type 2 1968 to 1979, this eliminates movement of the main shaft bearing and aids in maintaining the alignment of the gears on the main and pinion shfts to give the gears FULL CONTACT, which reduces the chance of failure.

There is a lot of discussion (ARGUMENT) on how to install this. We feel that you should simply remove 1mm off the gasket surface of the nose cone. A lot of guys don't do this and it creates 2 problems. First, it moves your engine back 1mm. Secondly, now the backup light switch is 1mm farther from the reverse shift rod, so it MAY not connect every time you are in reverse. So skimming the nose cone is a wise move. It only takes 20 minutes or so, with some sand paper and a sheet of glass to keep it flat.