Which alt to use ?

I dislike "one wire" for several reasons. They are more difficult to deal with with trunk mount batteries. Some of them don't excite until they are "revved" above a certain shaft RPM. And they require MUCH larger charge wires for proper operation, because the "one" wire IS the sense wire

Older GM 2 wire: Be careful. You cannot simply apply key-switched power to the excitation on the older one. This is the lamp circuit and you need at least a diode. It may work for awhile but "one day" conditions will happen that the diode trio will blow up because there is no isolation. Other than that, they worked fine

I prefer external regulator for ease of troubleshooting, but that is my preference. You must make sure the VR is grounded to "same as" battery and little drop in harness for proper charge voltage. Same for "3 wire" integral regulator.