If you don't live in a cold climate what's the advantage of anty freeze , .I ran a bunch of rental cars and after having a heater core corrode through (on the shop hack )I just used straight water ,When I restored my first FH car in the 80 s we welded up the alunmium heads after a few years we were on a run and engine started to run rough we found that the weld had corroded away this was due to the anty freeze most likely being past its use by date .after doing this twice I went to iron heads .Yes the antifreeze has additive's in it like for the ,pump lube ,water wetter ,anty rust but I don't think I would run it ,in a flathead .if you do at least change it every year its very corrosive , Its a big thing here to use soluble oil (lath cutting oil )in Model As ,as a lube and rust preventative ,a cup full of that will do the job .Ted