can i use any other tranfer case on my 83 GL wagon?? mind you that i have a 4 speed and i want to put a 5 speed in soon

The "transfer case" is an integral part of the transmission, not a separate ("divorced") unit. Several people here have added a "divorced" transfer case to their Subarus, but AFAIK it also requires at least a mild suspension "lift" to provide ground clearance.

Competing philosophys on the minimum lift, some say 6 some say 8, and both have their good reasons. But a Tcase is a major undertaking that only comes after a few other major ones. You can look at my website http://www.subarubrat.com under MY BRAT mods and then see the Tcase install, lots of welding and fabbing.

 

But, I think your question is more about going from a 4 spd to 5 spd tranny, that is easier to answer by saying that the "Tcase" is internal to the tranny and that a tranny swap is all that is needed.