For an 800 HP application that tranny will last just fine. I don't know the seller but that is a Tranzact VB and I had great luck with them.

The only issue I see is you need a billet front drum for absolute sure. A billet front planet and a hardened rear shaft would be a plus but you do not need it.

You commented on the bolt in sprag. That is not necessarily a good thing. A bolt in sprag is installed either because someone is told they need one or they spun the stock one and ruined the holding capability of the case when the old one spun.

Leon