Al 38 Master brake wheel cylinders on ebay are for trucks what gives ? pictures look the same as what removed from 38 car,working on rear now.

Don't know for sure but suspect the truck wheel cylinders have a larger bore than 1/2 ton or passenger.

If you buy NOS cylinders from ebay or elsewhere it's advisable to put a kit in them. 70 year old rubber is likely not viable.

Have you tried NAPA?

Rock Auto Has Them

So Does Napa.