FWIW-my Dad had a '51 Chevy car with the 216. All he ever ran in that car was Prestone mixed with well water. When he shut it down in'61, it had well over 100,000 miles on it and had never had any problems with the cooling system. Having said that, my thinking is like the old cowboy at the dance hall---ya gotta dance with the one what brung ya!
