Here's two pictures of the external alternator mod I did to my '85 Limited Edition. Behind all the plastic is a 55 amp car alternator. Just need to take your time and be patient.
If you are going to do the mod in a weekend, probably less than a stellar look. I took almost three weeks to work on mine, test and trial method to minimize the impact and keep a good look.
The alternator is directly behind the two black vents in the first picture, I wasn't willing to cut any of the plastic - took the picture before I hooked up the second driving light.
Don't need a large alternator, a 30/40 amp is more than sufficient for the operation of a carb 1000/1100/1200 Gold Wing.
A 40 amp is more than sufficient for an '85/'86 fuel injected Gold Wing: