I have observed over the last 25 years that many overheating complaints are either overstated or caused by other engine issues.
First How do you know you are overheating? Are you dumping coolant all over the ground? Just becasue you standard gauge says hot is often not a true indicator.I suggest a second sender installed in the other cylinder head and a quality aftermarket gauge.
Second Endemically the castin in the fifties was not as precise as later say in the 60s. Questions are: has your engine been rebuilt and if so bored out how much? Are all your other engine systems and components working properly? Are you using a Mallory distributor? There are mot questions but in answer to the above; If rebuilt,how much are the cylinders overbored? this iis not a common problem but does occur when the cylinder walls are thin. A faulty vacuum advnce can run the engine hot, timing an engine with a few miles on it to the timing mrks can be incorrect. This can result in poor performance and other associated problems. I suggest timing by vacuum. Have you recently or ever adjusted the valves? an out of adjustment rocker arm can result in a burned valve and a poorly and perhaps hot running engine.is your engine's carburetor
jetted properly. A common change to a too large "modern" carburetor
. For instance an Edelbrock
600c.f.m or greater is overkill. That carburetor
out of the box is for a Chevrolet 350c.i. engine A 500 c.f.m carburetor
is much closer to your actual needs.
The sum of my comments is: make sure all your other engine systems are correct before spending a lot of money on fixes tht may help but not solve your problems. I have a C code '57. It runs consistently 190 to 195 at extended distances at 70 to 75 m.p.h. with the air conditioning on. In town in traffic no real problems. Only occassionally in mid summer climbing a very long grade like Altamont have I ever had to turn the air-conditioning off. I took advice from Walt Nuckels and Jimmy Skoggins years ago to have a cool runnig engine and have been happy ever since. I also run a standard radiator
and distilled water.