David,
I see we almost overlapped our responses. Good idea about sleeving a 38 cyl; much easier to find. A 22 ejector star might be the one to reconfigure. I would retain the recessed rim feature if for no other reasons than it might be easier to find and he could readily tell the cylinders apart.
I was thinking a phone call to Chicoine could get him some great advice and suggestions:
oldwestgunsmith.com