@72bluNblu, My 66 Valiant wagon had a factory installed 16:1 steering box and 245/60/14 tires. It was very heavy but responsive driving down the road. It just wasn’t for me.
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...
Try Jeff at JC Auto Restoration, Inc. | Vintage MoPar Auto Parts & Restoration . He has a US 65 Valiant wagon and he has probably collected a few extras.