Beginning in the late 40’s, with the disappearance of numerous independent brands, more cars began using wholly proprietary parts. One thing to keep in mind when restoring an American Austin or Bantam is that their parts bin was not confined to what was built in their Butler factory. You would be surprised at how many of those parts could be obtained at a local hardware store or which were common with obsolete Fords.
Despite the fact that all American Austins utilized a similar headlight housing, there were a surprising number of differences over the six year production run (depending how you add them up). One static attribute of the lights was their inclusion of a single socket assembly that is remarkably similar to the ones used in 1928-1929 Ford Model A headlights.
Here is a photo of an original pair of headlights:
Click here to see the listing: American Austin Parabeam Headlights
Here is a photo of a new reproduction Model A socket assembly:
Click here to see the listing: Headligt socket
They do look quite close, the only way to know for sure is to pick up a set and see how they fit. I believe MACs has a decent return policy if the parts do not meet your expectations.