If I were to get a 20x8.5 wheel with 5.5 backspacing then how much outside dish would I have?Would it be 2 inches cause the center of the wheel is at least an inch thick?

It depends on the wheel. Some centers have more curve to the face profile to yield a bigger lip, or could have a longer (thick) mounting pad that would reduce the size of the lip. You can usually figure on around 2-inch thickness from mounting pad to the face where the center meets the hoop. For the 20x8.5 with 5.5 backspace that would give about a 2-inch lip.

It's an Intro wheel if that helps.Thanks for the helpful info Jeff.