If you leave the knuckle alone and just replace the steering box with a rack, your ackerman will not be changed at all since that has to do with your wheelbase, the angles between the ball joints and the pivot of the TRE. Your turning radius can be kept the same or even improved if you use a rack that has the same or move travel than the stock steering box setup.

Are you looking to custom mount a rack in your car? or do you just want advise on what aftermarket front end to get. I can help with making your own setup but its more of a take-your-pick for the aftermarket stuff