1966 GMC Dana 44 problems

[60-66]

I have a 66 GMC Suburban and Im on my second rear axle. Ive blown the spider gears in both with my stock 400 SB and TH 350. ( last night in the burn out pit at a local car gathering at a friends ) Each time this was NOT from excessive amount of that abuse, this rear ends first ! Anyway, Im looking for a better rear axle. Any ideas ? Thinking of a 1971-1972 5 lug 12 bolt so I can match up with the 5 lug front discs. Plus its a GMC with leaf springs to add to the search .