If you have a married transfercase/tranny then it attaches to the back of the transfer case. If you have a divorced transfercase/tranny then you can attach it either to the tranny or transfercase. As far as the adapter swap goes, you have to pay for each adapter but Gearvenders will store it for you as they will only let you have one adapter per unit at a time. If you get one with the wrong adapter for your application, you will have to send them the wrong one and pay for the new one. If you ever want to change back to the oner you sent them, they will trade you for the one you have at just the cost of shipping. You never have to but an adapter twice. If you ask Gearvenders, they do not make a version to mount between a married transfercase/tranny.