ok here is a dumb question the rule book says that the front and rear brake drums may not be interchanged aren't the rear drums splined for stub shafts if thats the case you cant change them or are they talking bout wide five and four lug drums?

You are correct in that it is a weird rule. I am sure back in the day someone found a way to make front or rear drums interchange.

I think its a reference to the four or five lug drums

Why would front and rear brake drums have different lug patterns?

I beleive it means, both the front and rear drums may not be interchanged. like, you cannot take the front and rear drums off your 1974 and replace them with a set of wide five. If you recall, Bensons class 11 had done that........not that you would interchange the front with the backs but rather the front and back may not be interchanged with a different year. four to five or five to four.............

OK Thank You