I've not gone looking for tires yet, because I still have the ones that Grandpa had on there when he parked it.
You can get inner tubs with a 45° angle. Any good tire shop (or even a rubber supplier) should be able to provide these to you.
I'm not going to tell you to dump the bias tires and go with radials, but I am going to tell you to dump the wheels.
I know you're trying to be totally original, but I would dump the split rims for something else. Most tire shops won't touch them, and doing the tire work yourself with them can be LETHAL if you do not know EXACTLY WHAT YOU ARE DOING.
I cannot stress that enough.
I know that they had solid rims with lock rings on the '46 model year 3600, and these are far less dangerous. These will fit on your hubs and you can have tires fitted on them anywhere you like. Modern 8 bolt wheels fit also; you can drill in some holes for the little hubcap holder springs off of your split rims, for the vintage look.
