I think OD started w/ the open drive line [maybe before, but they'd be different cases], the earlier ones were not syncro 1st, that started w/ the change in the regular 3spd in 68 [muncie as 'standard', saginaw the HD option] - not sure how long they lasted, but at least thru the 70's - not common tho - rebuild and parts view info should be in the shop manual for late 60's cars, so it says in my 67 truck manual
Bill
