It sure sounds like a heat issue as all fuel lines have been checked/replaced. Insulating or re-routing hot areas may help. Also, no harm in trying the Holly pump but I don't guess that is the issue. Also, per my understanding, a Holly type carb is happy up to 9 psi. 11 psi is really pushing it and may overpower the float and needle valve and make bigger problems. Carter/Edelbrock carbs do not like more than 5 psi.

The two robust fixes I know of are a return style fuel system or an electric pump mounted on the frame rail where it is cool. I have used a booster electric pump to solve this problem. There are several threads on this, many approaches and many opinions.