f.booth;
I have those 3 piece rims on my truck and have had some of the same problems finding any sort of replacement for them. The 19.5 inch seem to be the best option (short of replacing the axle) but I haven't found a set of 6 anywhere around here. I've been told that they were/are pretty common on Chevy delivery vans, too. I've been able to find the 19.5 inch rims but they're all the 10 bolt pattern; not the 8-bolt 6.5-inch that are on my truck.
I did have my tires dismounted about a month ago and the tire shop said they seemed to be in good shape and I should be able to put them back on. I'm planning to have them sandblasted and repainted (as long as they look OK once the rust is off them) in the near future.
I was able to find the 18 inch tires at a local tire shop for around $150 each (tire, tube and flap) plus mounting and balancing (around $15 each). From what I've seen for 19.5 inch rims and tires for sale, that's not too bad a price and I don't have to do much chasing around to get the stuff I need.
Let me know if you find something cheaper or easier. I'm interested in your solution.