Can I ask you why? What do you think you will gain?
This question gets beat to death on a lot of boards like this and there is really nothing to gain from this swap... It MIGHT save a few pounds but that is it. How much does a couple lbs really matter on a street car?
I want you to know right up front that swapping from a recirc ball box to a R&P is not an easy job. To do it correctly the inner tie rod points, as well as the height of the rack, MUST be in the correct relationship to the upper and lower control arm inner pivots to prevent drastic bumpsteer during suspension travel. Using an off the shelf rack, which was designed for another suspension, is not going to get you there. Bumpsteer, ackerman, turning radius, etc. will all be affected.
When I design a suspension I START with the rack and inner pivot points and build out from there. This allows me to put the control arm inner pivots where they need to be to work with the rack. Adding a rack to a current suspension is putting the cart before the horse. Unless you have the ability to redesign AND rebuild your entire suspension to work with the rack of your choice you will never have the handling and cornering abilities of the stock steering box and you will not like driving your "improved" car or truck...
Mark