I have a 1940 Chevy with a 302 GMC engine with AC. It has the same diameter pulley as the original. The 40 Chevy radiator is much narrower than your 53 Chevy's and has an electric fan on the front of the radiator. With that setup my engine did over heat on really hot days pulling up long hills at high speed.
I had a radiator guy replace my 2 coil copper core with a 3 coil. And, I built a sheet metal shroud to duct the air from the upper grill into the upper radiator core, instead of just escaping blowing into engine compartment. Some cars come with this shroud but not the 40 Chevy. Your 53 may already have a shroud. Anyway, my overheating problem went away with these 2 mods.
