Here's a resource for tire inflation. It may contain your tire size, although may not be entirely valid if you've mounted the tires on skinnier rims than the size calls for. It involves weighing each axle, then inflating to the required load. Modern tires on an AD truck would typically have much higher load capacity than needed. Note that this is a Toyo document, but that doesn't matter, as the tire size is what dictates.
Toyo Load/Inflation tables


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.