Try Barry's Tire Tech:
www.barrystiretech.com/vintagetireexchange.html There's also a good site called "Vintage Car Connection"
www.vintagecarconnection.com/vintage_tire_size_conversion_chart.htmI found a good excel sheet, but my notes don't tell me which site I found it on. One thing I learned from my research is that not all "old" sizes have been carried over. You will likely have to pick something that's close based on availability, or buy a specific antique tire (still available).
I opted for modern tubeless radials for a variety of reasons. Not the least of which is that it's one way to improve the performance of a 60 year old steering and suspension system.
Good luck and have fun.