well,there are choices for rack and pinion for 71-73 mustangs. Trust me,I've been doing extensive research and talking to alot of people in the business. The cheapest one would be from Fatman Fabrications which comes as a kit which includes a new lower cradle to support a-arms,99-04 stang spindles ans struts and an escort steering rack.
upper control arms and strut rods are deleted. Cost is around $2k and you'll need to supply,the rack,spindles,struts and a few other misc things. Plus,you'll need to invest in an aftermarket steering column although, the stock column will work with a ton of modification. The things I don't like about the kit are,its throw together with parts from other cars and can't possibly be engineered properly for the car. Which means you won't know what to expect until after you've bought it and put it on the car and or lose control while driving because of Bumpsteer,loss of turn radius,Ackerman effect,etc. I Highly recommend you contact them for the install sheets before purchasing because after you see all the hacking you need to do to the column and shock towers,the escort steering rack needs to be modified,ties rods have to be extended and threads have to be extended,spindles turn arms have to be cut off and lower boss' have to be ground to keep lower balljoint boot from tearing and the list goes on. Once you see all bullcrap you'll have to do,you'll most likely change your mind.
The second choice is,RRS (australian company) has just announced a rack and pinion set up for the 71-73 mustangs in either left or right hand drive configurations. Cost is $2500 plus shipping and doesn't include pump,lines,etc.,thats all extra. Haven't asked them if the kit if designed for they're strut
suspension or if it will work with stock
suspension. I'm hoping it will work with stock
suspension but,waiting to hear back from them to confirm. At this point,I want to stick with a readily available header so,I might buy the RRS kit for my car. I don't want to make custom headers and then if they rust or break down the road,I have to build another set. I don't like the idea of spending $2500+ for rack and pinion either.....