I was having the same issue, I relocated the fuel line from between the timing civer and PS pump, it was runing up this area.
In 1967, my Car had a Carter AFB the fuel line went around the PS pump and up and 90'd to the Carb it is steel all the way up to the carb except for the filter, and my problem seemed to go away, also I found several vacuum leaks. Insulating is a good idea too.
I also replaced the Water Pump with a new one(not rebuilt) had a better impeller on it and closed up the gap between the impeller and back plate as I was instructed by everyone here.