The steering rack on this unit is mounted on the engine firewall. If you don’t know where it’s located at you are in for a lot-o-good trouble. Might be better if you took it to a shop. For the simple reason of sanity!
the rack is very simple for someone who is mechanically inclined. all 79+ mustangs have the rack mounted to the front of the engine cradle. there are 2 bolts that hold it to the front of the cradle, or K-member as its known in the ford community, then the power steering lines and the outer tie rods. there is a lock bolt on the steering shaft also. they are NOT on the firewall, anyone who has done any work on newer mustangs would have known that. just not that you will need an alignment after, and make sure that you properly bleed the power steering, as running the pump dry will destroy it.
as for the hp rating, what kind of BBK headers, there are shorty and long tube. also does it have cats or no? those will all make a difference.