Make a patch plate of 1/8" lite plywood just a little larger than the firewall hole. Figure out where you want the the fuel lines to be and drill snug holes in appropriate locations in patch plate. If holes are snug, there will be no vibration/chafe issue. Attach patch plate to firewall exterior with med CA or epoxy. Fuel proof area (inside and outside) when done. DONE. Your tank is fine, don't reinvent the wheel. The patch plate I suggested will keep excess fuel residue out of the interior. Pad tank with foam to reduce vibration and keep it where you want it.