The Firestone wheels were used for 20 years or better. However, 2 piece or 3 piece motor wheel was used during the same period and they are interchangeable. One of my old 2 tons has the RH 5 wheels which I would like to replace, but haven't found anything near where I live in Texas. I have changed the dangerous kind, but I wouldn't recommend anyone to do this that didn't grow up with them. Watch things like Craigslist or post a parts wanted. I am near Vancouver at the moment and there are lots of old farm trucks in this area. I would think you could find something. I also would recommend you measure again.