Can't answer for the Op on his thoughts and plans. But I can say that as far as I know every attempt to modify the original K-frame to add rack and pinion has been an utter failure. I certainly haven't seen everything, but that's what I remember.
If rack and pinion steering is a must, I would suggest you look at a full aftermarket suspension like
@HemiDenny's kit or similar. The why's and options beyond the Op's thoughts are for a different thread though.
