I have a 1971 D100 with a low mileage 360 I would give you. 1971(first year) to 1974 or 5 360's are high in nickle content and as strong as the 340's were. However if you are open to later blocks, a Magnum would be the way to go because of the roller lifters. Some pre-Magnums had rollers in the 80's.
You should be worrying about the integrity of the block if you are going to be under 500 HP anyway. Then you might want to look at a stronger block and main girdle.
BTW, the truck is nearly a complet basket case due to rust. I always heard Dodge trucks would rust to the ground before they quit running and I guess they were right.