protouring "rake" causing issues with fuel tank utilization

I know the title is long but it had to be.

I have a Hot Rod City garage AL tank in my protouring 69 Cuda. I finally got it to that point of being a daily driver but I have been unable to get fuel gauge to work closer than being 1/4 tank off. That doesn't concern me as much as I'm not able to use the last 4 gallons of gas in my tank. I have had 3 episodes when I have ran fully out of gas needing a tow to the gas station and then filled up to find out I still had approx 4 gallons in the tank. It seams that I can't utilize the last 4 gallons in my tank. I have looked at all options and I have one additional question, could the protouring "rake" of my car being totally flat not allow the pump to utilize the last 4 gallons of fuel in my tank?