My four speed is at the shop also.
The guy told me that the internal gears were bad, and could not be located anywhere.
I did a search myself and could not find any.
I went and bought another four speed, a RAD-K, and he said the gears were okay in that one.
Funny though, the rebuild kits with synchros and seals are still readily available.
Grant also told me he hasn't worked on one of those in many years, and was suprised to see one come in, let alone two!