Tranny countershaft replacement

1950 el - 4 speed stock tranny.

The countershaft shows some minor wear where the needle bearings run.
I read somewhere that 1976 to ? countershaft could be used with the roller bearings for those years.
Are the countershaft bushing in later model the same as the 50's or
will they have to be replaced also?

I would be too lucky if someone made a replacement kit.
SJ