Fuel Tanks

[Black H1]

Looking for some advice or answers, a friend of mine has an 89 Humvee that he converted from the 6.2 to a 454. We were wheeling last weekend in the most amazing terrain and it was 107 degrees. His tank would not vent and he continuosly faced a vapor lock situation. Here is the question. With the cahnge from diesel to gas, is it necessary to also change the fuel tank? What would be the recommendation to move to and yes, he has a venting cap, that did not work. I do not know if it was the extreme heat or the near vertical walls that we were scaling that contributed to the engine cutting out, but we are curious and will change the tank if necessary. thanks