You need to get under the vehicle, take photos and find any numbers cast into the side of the box.
A useful website for basic identification is Novak transmissions, great resource.
As it is an AMC360 the number of possible cheap boxes that could be fitted without specialist adapters is quite low. It is more likely to have a 3 speed that came with the AMC V8. A possible is a Borg Warner T15 3 speed (quite strong and capable) - on the passsenger side cast in would be the numbers T15 or 1307, or 13-07-065-901
BagusJeep lives in Bali, the Land of Temples.
With a Jeep every prayer counts.
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1995 Cherokee 4.0 - CHEROKEE