19.5" wheels, like 22.5", and 24.5", and even 17.5" will always be tubeless. It's the whole number sizes that were originally tube type, then the half sizes came out as the tubeless wheels. This is still true for the wheels and tires we're interested in for our old trucks.
These days car and pickup tires with whole inch rim diameters are also tubeless. That's an exception to the old rule of half size wheels being tubeless and is no help for our old wheels and tires.
Grigg
