I don't take any chances with the ethinol gas...I always use the 2 year dose of Sta-Bil with all gas I put into my car-I believe that my recently rebuilt/restored fuel pump and 4100 carb were done with materials that will be ok with this crap gasoline we are forced to use today.
Something else you might want to consider is the addition of a spring in your lower radiator hose....these cars originally had them and the repro hoses don't come with them but the springs are available separatly now, I had a simmiliar problem like you described and my engine was running a bit warm, I added the spring and all is well now.