A flathead Ford cast iron block with aluminum heads is exactly the same as most modern 4-cylinder engines. A regular old mixture of 50/50 antifreeze works just fine. That is what the manufacturers recommend. You will not any signs of electrolysis on the modern engines heads when they are removed. Use modern composite head gaskets. Don'r spray them with copper coat or anything else. They have sealer on them already from the factory. New Edelbrock heads recommend Felpro composite gaskets be used. Because the cast iron block and the aluminum heads expand and contract at different rates automotive manufacturers have engineered composite gaskets to solve the problem. The combination of cast iron, aluminum heads and copper head gaskets will cause electrolysis and eat up your heads. There is no reason to use copper gaskets on a street engine. They are for severe cylinder pressures like in race cars where the heads are coming off almost every race.
Speaking of electrolysis. If you look at the garden hoses everybody is selling now they have aluminum fittings on the ends instead of brass. I go through hoses like crazy around here with eight hose bibs. With an aluminum hose fitting screwed onto the brass hose bid after about a month I cannot break the bond between the aluminum fitting and the brass hose bib, electrolysis has welded them together. I have one hose attached a soldered copper fitting from the house that I'm going to have to cut off. Its the same thing if I connect a hose with a brass end to one with an aluminum end. After awhile I end up having to cut the connection out. You cannot leave them screwed together for more than a few days. The fittings will just crush under the force of using channel locks while trying to get them to separate. Do not buy those hoses with the aluminum ends, that's about all there is anymore. I swear the Chinese do this stuff on purpose!