Join Date: Aug 2009
Location: Lakewood, Colorado, USA
Model: '06 GL1800
The 1988 alternator mounting is slightly different than the later years' mounting, which is why you'll not find many listed.
Your '88 alternator mounts using shouldered bolts. The shoulders on these bolts are used to position the alternator allowing the sealing o-ring to be more-equally compressed.
The later year alternators use dowel pins (OEM p/n 94301-10160 et sim, for the curious) in lieu of the shouldered bolts for the same effect.
That kinda explains the "why" you're not seein many listed.
A good work-around is to either have your unit rebuilt (as presented above) or to modify your mounting situation.Simply over-boring the mounting holes on the later model alternators will allow you to retain your '88's OEM mounting bolts. Some folks have also gone with changing to "normal" bolts to mount a later-year alternator onto these first-year bikes.
While, personally, I prefer to re-bore the alternator's holes a bit, choosing to change the bolts will allow you to "share" spare parts with other 1500 riders without road-side modification...