A lot of modern pickup trucks run 20" tubeless tires, but they're usually very low profile- - - - -wide tread with short sidewalls. They would probably look pretty ridiculous on a truck such as yours.
Jerry
I Agree Jerry, I'm looking at 245/70R20 but that doesn't excist it seems.. atleast not here in the Netherlands (don't forget I'm in Europe, different laws etc apply)
Found some chinese tire Goodride CR960A 245/70 R19.5 136/134M but thats 19,5" so that means starting over.
There are tons of military surplus tubeless tires out there, mostly Michelin’s but a couple other brands as well.
I guess Tony, but again..I'm not in the USA. I can find 11R20 militairy tires..but they're way to wide, and old

Are they 20" or 22.5"? I've never seen a 20" tubeless HD truck tires...You can also look for 6-lug Budd to Dayton Rim Adapters and then run 22.5 Tubeless Dayton's...or your 20' tires on Dayton's.
Hey Mike, yes we've had this discussion before

I can't find Dayton's here in Europe..and I don;t have the patience to wait for that one unicorn, because I need a rolling chassis to get moving along with the project. But if anybody knows of some Dayton's for sale, I do have a forwarding adress in Riverside, so I can look at shipping them over.
I'd love to go to 22,5, but the rims and tires here are ff'ing ridiculous in price..