I'm going to assume your rims are damaged due to be loaded with calcium, and are rusted out around the area of the hole the tubes valve stem comes through. There are some used one's out there in salvage yards, but that's not saying they aren't in the same condition of what you have. Here is a listof 14, in various salvage yards across the U.S.
Pardon Our Interruption ,and good one's will not be cheap, plus shipping if need be.
Depending on how far away from that hole they are damaged, as in, between where the rim attaches/spot welded to the pressed steel center, a decent welder could section you in a piece of good rim of the same size fairly easy, you just need to drill a new hole, for the valve stem to come through. It still can be done, if beyond where they attach, it will just take more work, and a maybe a better used rim. If more than that, buy a new blank, open center rim to match, cut the old one off, and weld anew rim onto the pressed steel center.
If it's a smaller area, just around the valve stem area, it can be repaired with multiple passes with a decent 110V mig welder, doing multiple passes, and grind off excess to get the desired repair. This is one I did on my Farmall 140 this Spring. Far from perfect on the outside, but good enough for who it is for. I made multiple passes, until I could fit apiece of 1/8" thick X 1" wide flat strap, and weld it in place for the flat spot in the rim for the valve stem to come through. I probably had 6 hours involved in this, welding, cooling, grinding, etc. etc. But, after pricing a new rim, and wasn't exactly oem style, I figured I had more time, than money. A good rainy day job in the shop. I figured less than $20 in consumables, between wire, gas, and wear on a grinding stone. A LOT less than a new rim..!!
It all depends on what you have available to you to work with. Pretty costly if you take it to a weld shop, but more than likely done right. If you have a buddy with a small MIG, the barter system can work well too, or cash to cover consumables, plus adult beverages, if they partake in them.
I bought this little Lincoln 110V MIG over 20 years ago, and I know it's paid for itself several times over just on what I saved doing repairs like this over the years. It seems a person never has enough tools, for every job. 40-some years of puttering around fixing old tractors, and I still find I need to pick up something to make a job easier, as time goes on.
But, back to sectioning a rim, I'm sure there are some YouTube video's on this type of repair. Might want to take a look. Just some food for thought... I did go to John Deere and found the part number for the MT rear rim. It's JD3001T. I did a Google search, and found a thread about a 435, which uses the same rim from 2012. At that time, used rims were fetching $465.00, and new were still available from John Deere for $1,000.00 a crack. I doubt new are available now, and I'm sure used have increased in price, but, you never know. You can always call the above salvage yards listed, and check.
