First off I love the truck man! I actually just posted about getting info on those front fenders because I want to try and mold them to make flares that match all around for tire coverage maybe that would work for you guys too.
Are your rims split rims or split ring rims? If split rims you couldnt give me a set to lower or raise the pressure in, split rings on the other hand aren't as terrible but I know people still dont like them especially when try to seat the tire for first time.
I'm not sure if bolt pattern is same but m939 trucks came with 11r20 goodyear G177 radials on them, split ring wheels with tubes but the tires themselves are made to be tubeless. You can find these tires pretty easy, I had them but went to 425's for flotation.
Your fronts remind me of the old armstrong M&S pattern, samson has them in 9.00-20 and 10.00-20 if you went back to 20's all around, they also make some aggressive tread 22.5's but not in a 9.00-22.5
https://simpletire.com/samson-10.0020-10069-2-tires
https://simpletire.com/samson-9.0020-90049-2-tires