Jd 300 mag side o-ring

[Timford]

Hi guys. Long time lurker,first time poster. I'm replacing the crank seals in a 75 300 with the kohler 292. There is supposed to be an o-ring on the mag side crankshaft and some shims. Mine had neither. The John Deere number of the o-ring is m64037. Does anyone have the dimensions of that o-ring? And where exactly does it go? Do you think I can get away without the shims? Thanks a lot.