Hot Fuel Lines
Beautiful car. Love the execution. I think you might be on the right track after looking at the cross member like jaba the hut pointed out. I would do everything in my power to relocate that section of fuel lines. Into the frame, through the frame to the outside of the frame (IF NHRA allows), whatever I could do. I don't think fuel percolation at the carburetor is possible with that intake. It has no exhaust heat cross over provision. Sometimes they even ice over. I've had a few do it. That said, I guess it wouldn't hurt to run the thick carburetor insulator gasket. Maybe that coupled with relocating the fuel lines will get it solved.