Thanks for that. The one that came off may have been from a B body - I took a trip to a Mopar friend's place yesterday and he showed me a few that looked really close to what I had, but even he was stumped by what it was from.
While walking around looking at things I mentioned I would've to convert one of my Darts from Federal to Saginaw but the original brackets were hard to find and repops were expensive, not to mention the pump, and he pops open an old Dart door, picked up a Saginaw still in its brackets and said something like "take it if you can use it". I've met some really nice guys doing this car thing.