Why do you have to get headers? Dip stick tube? You can also use the older cast iron manifolds.
What casting numbers did you use to determin 4 bolt main?
You should be using the entire accessory drives / pulleys of the motor that came out of the truck. All the brackets should bolt right to the older two piece rear main seal motor. For the power steering bracket you will need to fabricate a spacer to go between the front manifold bolt hole, and the bracket with headers. A piece of black iron pipe works well for this. The rest of the bracket bolts to the front of the head, and the water pump for the pivot bolt. The water pump should have a boss about 2" thick. The bracket goes over this both in front, and behind it. Long bolt goes through the bracket, through the water pump boss, and threads into the back side of the bracket that has a welded nut. That is the pivot point for belt adjustment.