You need to be a little more specific on the vehicle for a more accurate reply but this is my take from the information. First 40 lbs air is way to high, not even a new car from the factory used that much air pressure. Lowering it to 25-30 will increase your ride characteristics and be less jarring. The next is the tire construction, if you are running bias ply tires they are more likely to off track than radial due to sidewall construction. You did not indicate the condition of your steering box so we would have to assume that it is centered and adjusted correctly of free play.
Because your vehicle pulls on a crowned road I would check the toe of the vehicle first insuring it is in the "1/16th inch in" reading range. As the higher driver side tire hits the crown of the road the LF tire rises and the angle of the solid axle creates a greater positive camber on the inner tire RF. Because of the high air pressure, the tire is ballooned up so the center is taller than the outside edges. Because of the increased camber this produces a smaller rolling diameter on the outer edge and the tire favors the smaller diameter. Because the tire is slightly smaller in radius the smaller edge trys to spin faster and the additonal outward camber creates an effect that rolls the tire away from the center line of the car which you interperet as a pull to the right effect. I think just lowering the air pressure may help your issue so the tire sqauts a little and takes away some of the rigidity of the tire. This will lower the camber effect, even the tire diameter and maybe reduce the right pull.
