Torco is good stuff, so good Merc recommends it in the #6 drive. Standard Merc products should be good enough for an Alpha. You're not running any excessive amount of hp or anything that drive can't handle. Not that the Alpha is particularly strong anyways, my biggest concern with that drive is to make sure it's sealed properly and doesn't take in any water. If your drive shaft belows ever leaks your drive will take in water and die a quick death. The seal will hold drive oil in but not keep water out.