We are fighting this same issue with our 69 FB (469 auto 3.55 rear). The return line runs parallel to the passengerside manifold. The fuel line crosses the exhaust at the rear passenger tailpipe tank area, and at the back of the passenger wheel area. We have had our long branch manifolds ceramic coated, wrapped our pipes front to rear in header wrap, and run both the supply and return lines thru insulated fire sleeve. Hopefully we will get it running again by sunday to see if it resolves the issue.
We still will pick up heat from the mechanical fuel pump. I measured the temps during vapor lock under our car. Fuer pump top 189F, lower section 150F, exhaust manifolds 511F, floor pans 189F, fuel line next to passenger exhaust manifold 289F, exhaust pipes 250F, mufflers 150F, outside temp 88F.
