[Jeff Lee]

Mark Williams sells the caps you want. I would think they are only neccessary if you have a t-brake or stick. I've known guys that run an 8 3/4 with these caps with both a stick and t-brake and they hold up very well. For your application it's probably overkill. If you get one or both caps you will need to align hone the case. At the very least I would get the billet spanners. They move less and maintain the side-play clearance.