There used to be a place in eastern Washington that did exactly this-you sent them your 20" FR5 widowmakers, and they cut the centers out and welded them into 22.5" rims so you had modern wheels that kept the original look. If they were still in business I'd do this with my old 20" rims, however as far as I know they aren't, so I just bought new 22.5" wheels. They're a little bit dorky looking, but take modern radial rubber and also won't randomly explode and kill me while I'm working on the rig :-)
Interesting. I did see a YouTube video where someone did something similar for a smaller truck. He cut the center out of both old and new, then squared up and welded them together.
The difference with my set-up is the whole 10 bolt, pilot hub rim fits nicely inside the Dayton rim and self centers on the lip. IE: No precision tools or guess work needed.
Having said that, I might pull the the centers out an inch or two to get the backspacing more correct. (See picture) Or cut the lip off, slide the 10 hole further in, and flip it the way it was on originally. Also the donor Daytons are 9" rim so wider tires are required.
I do like the tire options available in 20" more than the 22.5.
