Beautiful truck. Congrats!
Years ago I put P225/75R15 radials with tubes and flaps on the original 2-piece wheels of my 50 Chevy 3600, and they ran great. They are not as tall as the bias 700-15 tires. And they were load range "B" tires. If you can get LT tires they will have a higher load rating, but I don't know about availability in that size.
