I don't know of any sources to pin down the voltage based on your VIN. It may be out there but I have never come across it. Maybe someone more knowledgable will jump in with some better info. I would guess if you have an alternator that someone has already converted it to 12 volt. My 62's are twelve volt, but from generators. There are some 6 volt alternators on the after market, don't think any went in as OE. You might try checking for a tag on the starter or pull some light bulbs and do a cross reference on their part numbers. Might give you some idea if your wagon has been switched to, or was built with a 12 volt system. Hope this is some help.