55 gallons of... ? And, how much additional weight will that add for you? Why 55 gallons? And, does that bring it above the rim on top (leaving some space for air above?
Just trying to follow how you got to that amount...
One of the things I remember about loading tires when I was deciding whether to or not (and what to use) is that you need to fill to a point where the fluid is above the rim. This ensures that the rims are [almost] never exposed to the air inside the tires and should drastically reduce any sort of corrosion that might occur.
+1 on the idea of filling with CaCl only if your tires have tubes. *However*... Add in the cost of removing the rim from the tractor, possible transport to a tire shop / dealer, unmounting the tire, purchasing the tube, installing the tube, and remounting the tire to the total cost. Once you've added all of that in, it will probably have a much higher actual cost than having someone drive out to you and fill with Rimguard (or something else).