I have to get new front tires for the 2WD TLB we just bought. I haven't even looked to get the tire size and designation yet. Obviously they are heavy duty items. Would a farm store sell them?
Just look through the yellow pages for tires, check out the ads for farm and industrial. Just about any tire store with a mobile truck carries them, and can come to your location and change them out. I usually deal with Goodyear.