[Rich in Tucson]

Please use antifreeze. I prefer standard ethylene glycol types that must be diluted with water, they have been used successfully on cast iron engines for many years. I am unaware of any advantages to "extended life" antifreezes for cast iron. I have seen the best rust protection with them and have found separate product anti-corrosion products to be worthless or near so, including soluble oil.

I live in Tucson, AZ where it never freezes, right? That is what most folks here believe however a typical winter has three days of consecutive 20° nights and most A's are stored in unheated garages, carports, or worse. I do not believe that you will find more freeze-cracked blocks anywhere than in Tucson, AZ because many A owners have been encouraged by the local "gurus" (?) to use plain water from a yard hose in their cooling system.... which by the way is full of hardness minerals that precipitate out and clog radiators. If you value your 87 or + year old piece of history, preservation should be foremost in your thoughts whenever you do anything to it.