At first glance, those look to be in pretty good condition. Once the tires are deflated and the beads are driven away from the rim flanges with a duckbill hammer or a slide hammer, you can find a small slot in the removable ring and pry part of it over the main wheel assembly, then gently tap it with a hammer. There is a relieved area of the ring that lets it slide sideways. Reassembly is the reverse of those operations once the new tire, tube, and inner liner are in place. Be sure to clean everything thoroughly with a wire brush in a drill motor or a small angle grinder and inspect the mating surfaces for distortion or rust damage. Brute force is not required, just a little patience and finesse. Put a few pounds of air pressure in the tube to seat the ring to the main wheel and either use several wraps of heavy chain around the wheel or an inflation cage (preferred) while bringing the tire up to full pressure. Millions of trucks ran hundreds of millions of miles with these rims, and most of them didn't go off like Fat Man or Little Boy and destroy whole cities. These days, we're living in a society of snowflakes who couldn't pour pee out of a boot without printed instructions on the heel.
Jerry
