I believe LMC makes a side fill. Once I get this truck finished I never intend to haul anything in the bed again. So the bed fill makes good sense. Also the reason for having the tank under the bed and filling from the top is to preserve a those beautiful curves the 3100 series has. As will has getting the fuel tank out from behind the back seat! Now that I think back of all those times I rode in that truck and my grandfather had is pipe glowing. Not sure what was more hazardous, the second smoke, or the chance we could have both been blow to pieces!
