Watch the heater box holes where the lines come through. They are different. You will have to re-drill one hole for the heater box to mount.
I think the easiest way around the brake booster, steering column, heater box, and wiring location problems is to cut the whole firewall out of a donor and weld it into the project truck.
You can cut your stock firewall out and leave a one inch frame around the perimeter and weld the donor wall to it.
As you get deeper into it you will see what I am talking about. If you need ideas just give me a holler.