Need help determining which hardware kit I should order..

So I am in the process of rebuilding the rear end on my car. It is an 8 3/4 741 and I have no idea what car it came out of originally. It was on the "donor" car when I bought it (1966 Barracuda) . I am trying to rebuild the drum brakes on it, but I don't even know where to begin to order the hardware kit, brake shoess, cylinder or whatever else I need to rebuild these..any ideas/help identifying what I need? What would I measure or how would I know which parts to order?