Hard to get good help these days. Only A-bodies used the "small sector" steering gear, and the last year for that was 1972, when they switched to the same "large sector" as our cars. I have both A & C body. The plumbing fittings also changed over the years, both inlet and return, so verify that. You can swap those between different gear boxes, but don't send your core back until sure you don't need those parts. If you get a Saginaw pump, you will need different brackets. Bouichillon and others sell them. I understand the Saginaw pump is more efficient, plus easier to find (GM). Our cars had the "TRW" pump. Around 1970(?), they changed to the similar-looking "Federal" or "Chrysler" pump, which I think continued when some cars got the Saginaw pump.
All the rack & pinion setups I have seen are part of a complete front-end replacement w/ coil-over springs that you weld to the frame rails. Very expensive (~$3000) and never seen one for a C-body. Anything you fabbed yourself would need strong supports off the K-member (difficult engineering design). If you get it wrong, you could get "bump steer" or the steering wheel turns reverse direction. The later might keep someone from stealing your car, and you'd get the hang of it eventually. Nothing wrong with Pitman arm steering. My 85 M-B uses that and it has good "road feel". I think most pickups still use Pitman arms.
