SM465 Countershaft

[K20rookie]

I took my SM465 and NP205 to a shop to have them rebuilt. Talked to the mechanic today, and he said the countershaft is cracked and his parts guy can't find a replacement. He says the one I have in there is slightly different than the ones he can find - apparently it has some sort of rubber damper on the countershaft. I read an article on fourwheeler.com that says early SM465s (68-70) "used rubber damper to cushion gears and keep down rattles. The rubber wore quickly and just made rattles worse, plus it took away spline engagement when compared to the later gear."

Have you guys ever heard of this? Can it just be replaced with a new style countershaft? Any advice you guys might have would be greatly appreciated.