I had my power steering box rebuilt about 13 years ago. The guy that rebuilt it changed some sort of valve or some other part that made the steering incredibly easy to turn which has always bugged me, much easier than typical vintage Mopar power steering. The guy has since gone out of business so I can't talk to him about it. So what I would like to ask is if anybody knows what the part is inside the box that controls how easy the steering is as I'd like to change it back? I know he changed this part by removing that small adjusting plate on the top of the steering box when he did it.

As far as I know the reaction springs are the main thing that control steering effort. Replacing those would require complete disassembly of the box.

The steering was normal until the guy changed the part I was trying to describe. I watched him change it and the steering was not the same thereafter.

What was changed are the pieces that control line pressure to the box. He increased the pressure which is why your box is easier to turn now. Normally you can buy a "kit" that has washers and springs that allow you to dial-in your pressure and steering "feel". Sounds like he went overboard.

6PAX - you may want to read the article Rick Ehrenberg wrote which may help you.
Ron

https://www.moparaction.com/2021/02/05/pump-it-down-2/