To fill a wheel opening you need tire height, but also proper ride height
As far as your question about other brands in 26x7.50 size, look up the actual height and section width of the MT 26x7.50 and plug it into the summit racing filter.
Great, did I mention I wanted the rims for all 4. I’m confused at which car originally ran 4.5x15? I know not an early a. Yet they are Chrysler rims small bolt pattern.