Thank you for the info crenwelge, very useful! Enough so, that I decided to annotate pictures of my wheels for figures to look at for discussion. Here they are:

http://s1378.photobucket.com/user/a...0%20Wheel%20Dimensions?sort=3&page=1

My intentions regarding the wheels are to keep similar size and change to wheel that will accept a tubeless/radial tire that way I will not have to worry about getting someone to change a tire. I know the wheels dimensions are important because I want to keep the same front and rear ends. Once I find the wheels I would like to then find tires that will roughly keep the same radius that is on there now, which is 38.5" in diameter.

Thanks for setting me straight on measurements crenwelge. As you can see in the photos you are right - I have 20" wheels. The outside of the rim is what I was measuring at 22.5". I took a rough measurement (without taking the tire off) and best I can tell is that the wheel width is 6". I am taking this measurement right where the 20" diameter curves to the horizontal plane. If I were to take the measurement with the tire off and at the inside edge of where it turns over could be 5.5" as noticed in Figure 3.

If I can move to radials would there be a preference between wheel width - 6" better than 5.5"? One easier to find than the other, especially considering common tire sizes?

Thanks again for all the advice here everyone!