I had one of the Enduralast alternators from Euro MotoElectics
on another bike, and can recommend it for the improved charging. The down side of the kit is the wiring. It just provides some general instruction, a handful of electrical connectors and some wire. You are left up to your skills to get it working.
The combined rectifier/regulator comes from a two wire Ducati system, and it just doesn't mate into the two component Bosch diode board + regulator system of the GS very well. Here's the rectifier/regulator from the kit.
I wanted the wiring for the new alternator to be reliable and clean so figured I'd need to make up some kind of custom wiring harness. I started by taking measurements of the existing engine wiring harness and whatever else would be needed to connect up the new regulator and came up with this harness drawing.
I think for maintenance it would be better to have connectors between the regulator and harness so the regulator could be easily replaced, but that would be complicated because the wires to the alternator need a high AC current rating, etc. For reliability I choose to wire the regulator directly into the engine harness.
The result for the most part is a direct replacement for the OE engine harness. The regulator needs switched power on the white wire which has no equivalent in the OE harness. My solution was to run another wire out along side the wires to the main harness connector and put on a blade connector that would need switched power from somewhere. I need to do some re-work on the main harness and I'll add in a new wire from switched power to connect up here.
In my old installation one of the connectors between the alternator and the regulator burned up. It happened on a trip to Baja, and the battery was ruined, so I had to finish the trip with a lot of push starts. I think that the AC current must get really high at times, then any resistance in the connectors will cause them to get hot and eventually burn up. As a quick fix while down in Baja I got some wire nuts from a hardware store. Those worked so well I left them on. Anyway, I want to have some good connectors there to avoid problems. For now, I put in a heavy duty terminal block. I'll attach it to the timing cover with a screw to hold it in place.