I know if you have 6 cylinder you have to get p/s set up for that. I don't think that a 8 cly. set up will work w/o mods. If you want a better steering system and stay with non p/s try a quick ratio steering it may be cheaper. Check on this link:
www.mustangdepot.com . They have a couple different choices to choose from.
I think this might help you!!!!
I have manual rack w/quicker ratio and it feels almost like p/s