Scott, not sure exactly what you want. You wrote 'mag body' but, they are not all the same.
If you are looking for a Mallory Pontiac mag base, here is a link for you. They bought out Mallory a few years back.
Mallory used to offer a Pontiac base with a tach drive. I have one in my collection , would consider selling it. It is unused, just has some shelf wear.
Here is the link-
https://fuelinjectionent.myshopify.c...55-lower-drive