To get a better road feel "feel more like today's cars" all you have to do is install a newer steering gear box off of a 1985 and up GM car or a Ford or Jeep because they all use the same GM Saginaw gear box that are interchangeable (sort of). This of course assumes you have a 1965 and up Impala.
If you have a 1958-'64 you need a Corvette gear box from 1963-'82 which has a faster ratio. From 1958-'64 on the full size Chevy, Corvette and a lot of light pick-ups the power assist was just that a hydraulic slave cylinder attached to the frame and the tie rod controlled by a spool valve inside the steering gear box. The hydraulic ram has six connections and two hoses that are prone to leaking fluid not to mention the cylinder seal going bad with time. It was a first attempt and only included because they desired those sales to little old ladies who couldn't parallel park without power assist. The Corvette needed power assist to be able to throw those huge 6.75-15 bias ply tires (78% profile) from steering lock to steering lock while road racing 200 miles at a time (Sunday Drivers).
Like I said in 1965 Saginaw gear division of GM introduced the 600 series and the smaller 800 series (and the 500 series manual) gear boxes. They have four possible bolt holes on the case of which only three are used to attach it to the frame. Saginaw sold the gear box to Ford and Chrysler which also used them on their cars because they were the newest solution to an expensive problem. Because it is a GM part it interchanges from pick-up, Jeep, Ford Galaxy to Impala from 1965 through 2004 when the factory went to a rack and pinion design on the Silverado light truck series.
You will pay more if you attempt to buy a box off of a Z/28, Firebird or a Monte Carlo SS. The same quick ratio box was used by Pontiac on some of their medium sized cars (A-bodies), Jeeps, and on all Chevy full size police cars (and on Nova Police cars as well). You can check on line for a list of donor vehicles that do not have the "High Performance" "sporty car" premium price.
I say sort of interchange because in 1985 GM had gone Metric and sealed the power steering hoses with O-rings. You can buy a new hose with mixed ends (metric on one end and English on the other), or buy an adapter to use an English SAE compression fitting in a metric O-ring steering box.
Most rack and pinion kits use a rack off of a Ford Pinto (also known as a Ford Mustang II). Both of these cars were a little over one ton in weight and are too short to work well with the bigger (wider track) and much heavier full size Impala. This is why a lot of people have issues with the alignment and bump steer when they switch over. If you question this info log onto our sister Board Team Camaro and read old posts from people who have tried and removed aftermarket rack and pinion kits.
Remember car mags live off of advertising sales revenue. It isn't in their best interest to mention any thing bad about rack and pinion kits sold in their magazines even if it could kill you. They are only going to mention how light they are and how fast the wheels can be turned from side to side with the car still on the lift. They generally end every article with the disclaimer "we are going to get back with you and tell you how great this kit is right after we have the front end aligned", but they never do mention any of the problems they experience trying to align the car or how bad those kits are in handling for some reason.