8BA Flathead overheating on highway

[FlatheadTed]

What fan arrangement Are You running ?You need to run a stock fan like early fords came out with they move a lot more air and this air needs to move through at speed ,don't rely on a electric fan alone you can run a electric fan on the front down low but this can parsley block the air flow so you run the stock fan set up or the equivalent plastic one with mutable blades with even a shroud that will pull the air past it .As been said It sounds like your Radiator is not adequate your motor needs more cooling than the others you compared it with, As a test try and run it at a fast idle until the tempt comes right up then place a 13" house fan in front this should start dropping the temp down if it does that will show you that air flow will do it . Ted