Geez Steve, you change your tires more than I change my oil! Not sure about the no one can make a radial bigger than 38" thing, I think there's probably just not a big enough market. You can get 40, 42, and 44" radials if you go to a truck tire, however they're for 22.5 and 24.5" rims and are like load range G or so. An 11R24.5 is right about 44" tall. You could also get a 425/65R22.5, like used on the front of cement trucks. I also had the displeasure of delivering some radial tractor tires on a couple occasions that were for 48 and 52" rims, the tires were taller than me, and were over a grand a piece.
Pete
Pete
'83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
'97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd