Need Help with Charging System

Hello, My '68 Dart is not charging. I have the pre-1970 alternator and regulator. I replaced the alternator and it didn't solve the problem. Today I found that the alternator positive post (output) does not have voltage when the engine is off. Isn't that wire supposed to have 12V (part of the battery circuit) when to engine is not running? Any help or advice is appreciated.

Thanks,
John