Hmmm... Wonder if the one I have may have originally been for a B body. I saw another like yours on line with that base. Wonder if I can find just a base or perhaps fabricate one. Other than that, they look identical.
Yes, that's a correct Mopar tach. I think all the tachs had the base. There's a 67 GTX local here that has the tach. I'll try and see if he has the base. Just an FYI, the tach should work if you run the stock Mopar electronic ignition however it won't with the MSD. Multiple spark. You'll either have to modify the tach or run with an MSD or you'll have to run the MSD tach adapter.
I'm still digging around looking for the business card for the guy who worked on my tach.