Buying mud chains or swapping wheels and tires is a lot of $$$ to address an assumed problem that may or may not exist. If the rears are loaded, I would definitely try it in low range 4WD before spending any time or money on modifications. If the rears aren’t loaded, you’ll likely need to load them, but that’s relatively cheap and easy to do yourself (and undo yourself if you don’t want to keep them loaded). Also, if you normally run high pressure on the rears, drop it to 12lb to 15lb for the plowing. The R4’s lesser ability to shed mud due to stiffer sidewalls shouldn’t be a substantial factor. If you’re plowing in a mud hole you need to let it dry out before plowing anyway.
I’ve never run moldboard plows behind my L. I have run a pair of 16” moldboards behind a Farmall H. Of course the H is 2WD with R1’s and it pulls them well because that’s one of the jobs it was purpose designed to perform. I also know, in a variety of soil types and conditions, the drawbar pull on my L with loaded rears, FWA, and R4’s is substantially more than the drawbar on the H.
No, I can’t quantify the max drawbar for either tractor, but I know I had to upgrade some of the rigging we had for tree work because the L was busting rigging that was adequate for the H. Also know the L has moved a few things that the H couldn’t budge.
I’m quite sure R1’s will pull more than R4’s in dirt on the same tractor. That doesn’t mean you can’t pull a couple of moldboard plows with loaded R4’s aired down appropriately. I would sure give it a go before busting out the checkbook.
If you do need to spend money, mud chains for the rear are a good bit cheaper than new wheels and tires.