moser 12 bolt housing is a identical reproduction part. if anything it weighs a few pounds more. It can uses all stock parts. It is nearly impossible to identify differences.
there is a aftermarket 12 bolt from starnge or mark williams that has an entirely different look to it. That would not fit any criteria.

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The Moser is a direct replacement for the factory 12 bolt right down to the leaf spring perches. They also do dana 60's and ford 9's.

The Moser would be OK. You just can't put a 10 bolt in place of the 12 bolt in the Stock class. In the Stock Appearing class you could run the 10 bolt and you are 100% Legal.