If you are talking about 7.50x17, it was always a truck tire and I doubt that you will find white walls. They are not that hard to change. Most of the 17" were 3 piece rims. You knock the bead down with a duck bill hammer and remove the lock rim. Then knock the other side down. Put a lot of lubricant, either Ruglyde or just plain soapy water, on the rim. Walking around on the tire will help loosening it. Then you can knock the rim out of the tire. Be sure you push the stem in so it doesn't get caught. Most tire shops say they don't change them because they are dangerous. The truth is, they don't have anyone who knows how to change a tire that won't go on a tire changer. There are still tire shops in farming areas that change them pretty reasonably.