They used them in late sixties and early seventies grain trucks too, still fairly plentiful in midwest. You can probably fix your old top assembly. Try a penetrant named AeroKroil on the shift fork shafts. Its the best I have ever used. I will talk to my wifes uncle this weekend as I got some work to do for him. I would pester him tonight but he just got home from the hospital from getting two stents put in and being 81 years old I image it set him back a bit.
