I also had to do some customizing for the fuel tank. In fact, it would have been really hard to install it had I not ripped off the bottom
I installed it facing forward, with the lines running around the bottom to the firewall. I made a spacer ring out of 1/4" ply for the hole in the firewall so a fuel tank stopper fits in the hole. I attached the lines from the tank to that. I wanted to seal off the firewall, so sparay from the engine (there seems to always be a mess around the engine) doesnt get back into the body. Also, the back of the engine sits very close to the firewall, and I didnt want the fuel lines to kink or wear against an edge from bending sharply. (and I just thought the plug was kinda neat)