Again, they are not split rims, they are lock ring rims. Most automotive tire shops don't know the difference. As Los says go to a truck tire shop. They deal with this kind of rim all the time. You will need flaps and tubes. Size is pretty unique, I don't think you will find a easy more modern rim to swap. Stockton Wheel makes a updated replacement but big $$$$. as Los mentioned if they are in good shape it shouldn't be a big deal. You also might want to consider bias ply as finding the narrow size will be easier. I have 225x16 on my B1C and I wish I had gone with 215 instead. 265 are overkill. Stock bias is like a 6.00 or 6.50 which will crossover to 205 or 215 radial. Check the tire section in this page. https://p15-d24.com/page/p15d24/tech/enhancements.html/. WIth no power steering those big wide radials will be tough to steer at lower speeds.