Early models (1990 - march 1991) have an 85 amp alternator, its a AC Delco unit with an external cooling fan. It has its own proprietary plug. Wiring is the same though.
But yes it is possible to swap to the later model 91+ alternator. Its a 70 amp Mitsubishi built unit with an internal cooling fan. They're much easier to come by, and they can be had relatively inexpensively NEW on eBay. You will need the late model lower pivot bolt but otherwise (other than the plug) everything is the same. The new alt should have the correct pulley on it.
Belt is the same.