the control arms are easy enough, just swap out the old ones for what ever new ones you wish to purchase. you can get a complete front suspension kit from mustangs plus, or NPD, or other places.
as for rack and pinion steering, unless you are going to change the entire front suspension to something like a mustang ll style suspension, or on of the strut type front suspensions on the market, stay away from rack and pinion steering on an early mustang. better would be to swap to a new borgeson steering box instead.