Quick question for the Brain Trust re: A833 countershaft interchange

Hey all,

It's that time in my '72 Duster project when the transmission gets new bearings & seals. Of course, in taking it apart dumbass broke the key out of the end of the shaft :BangHead:

Application is a A833 OD iron case from a '76 Scamp. The ones I've found so far state they fit up to '74 but I'm wondering if that's because post '74 A833OD generally had aluminum cases. Will a countershaft that states fit for a 64-74 4 speed be the same as the OD cast iron transmission or am I SOL?

Thanks

Ken