When I was racing I did use big brother of 8 3/4 the stoud 9 1/4,did buy Moser axle and 8 3/4 axle end.
Sure-grip was cone-type,and it never fail.
8 3/4 spider gear and 9 1/4 spider gear are identical.
IF you are going to buy a new sure grip unit I would never buy the Auburn cone type either use the clutch style or the Trutrac , I would also use Dr diff as a supplier , great company to deal with