Steering ratio doubler advice.

Have you driven your car with manual steering? A-bodies in my opinion don't need power steering. My go-to manual steering is the 20:1. It's one full turn faster than the 24:1 but not as "heavy" feeling as the 16:1. Electric power steering? Why? Are you planning to upgrade your electrical system at the same time? Keep it simple. These cars in nearly stock form with new suspension and steering parts are great performing cars. Add heavier torsion bars, good performance shocks and sway bar to make it drive more modern.
Yes, years ago I manual steering swapped a '73 Scamp with a 318. I used 24:1 and the column from a Duster. The Scamp drove fine, and I don't remember it being it being to difficult to maneuver or park.
I am upgrading the electrical system with a complete harness and charging system from a '94 Dakota, along with the Magnum 5.2 from that truck. I'm also replacing the torsion bars with much heavier rate PST bars and KYB shocks.