After two years of looking at my assortment of mismatched interior door handles, and searching Fleabay every couple days trying to find factory Austin A10 handles and cranks. I finally gave up, and started looking for aftermarket handles and cranks.
I found some billet items on sale, and they came with several adapters for round, splined, and square shaft. The square shaft adapters were typical 30's sized square shaft American, so they were .390", but my shafts are .310", so I made up some angle shaped aluminum spacers to take up the difference.
The handles all match now, and they even have adjustment built in to index them all to the same orienetation!
And I've got 16 of those extra inserts to use for some other project!