IIWMM (if it were my money

) I would replace the ring and pinion as a set...if there's any contact issues with the old ring I think it will be magnified.
It would also be a good time to try to understand the failure mode...lube level got low or improper lube was used (??)
The 3500HD might use a different (heavier) axle all together from the typical GM 14 bolt "1 ton" axle...seems like Rockwell axles were used on the 3500HD IIRC as they had truck overall GVWs from 12000-15000 lbs.