Good deal. I guess you bought a used one? The only new ones on Ebay are the reg/rec for the DC. There's just universal ones listed for the AC.
The OE one I took off was still good, I just wanted something adjustable. I've got a couple of those Yamaha generic ones laying around that I've use, like the one on my YTM200 right now.
https://www.ebay.com/itm/Yamaha-Blaster-200-1988-2006-Voltage-Regulator/264731005927?hash=item3da33293e7:grgAAOSwFlhevb2r
The case is aluminum. They are one wire, so the case has to be grounded.
On the AC horns and turn signals, that's mostly old European stuff, so if you see something in the US that has that, it was probably a personal or small quantity import. Not worth bothering with, kind of like 6V systems, just upgrade and be done.
Yes, most of the trikes use seperate systems for the ignition and headlight, so they have two systems, but many of them use separate coils in the stator. If the lighting portion s out, you don't have to replace the whole stator, just that coil. That's my gripe with the XL600R and similar machines, any one of those going out requires the entire stator to be replaced.