They come with tabs.

 

If you are looking for a set of good used diff guards, Rover Doc on the LRRF has a set of nice front and rear guards similiar to QT's for $80 shipped which is a great deal.

 

Nothing wrong with a belly skid if you plan on doing some rock crawling. Not everything goes as planned when twisted up in the rocks, and you'll be glad to have it when something unplanned happens. Better to hit the skid than add a crack to your t-case housing/inspection cover.

Though, it makes it a pain when you have to do work in that area.