KINDA hard to read numbers on the inside with tires mounted!!!! Same goes for measuring with tires on!!!
If they are 5.5" it should be stamped to the right of the valve stem.
Of if '70 and newer would have a part number above the valve stem.
Again, asking for date codes? There should be numbers around the valve stem hole. Can you take close up pics? Do all 4 wheels have the same numbers?
Are you going to Carlisle?
That rust on the inside is likely due to someone using one of those liquid fix a flat tire repair crap. Thats why the bead area is still rust free/clean.