Mine's a SCLB, which comes max with the 36 gallon. I think a 48 gallon came standard on other packages, but I'm not sure if it would bolt up. There is space in front of the 36 gallon to put another small tank (probably 5-8 gallons.

I have already confirmed the Titan diesel tanks will not work even if I swap the fuel pump, etc. Different standards. Yeah, it'll hold gas, but the pressures for gas and integration with the evap system are different so I'll get codes or fueling issues.

@WE3ZS thanks for the suggestion for the Excursion tank. I'll look into that. I'm not afraid of some minor fabrication if it will keep this weight low and boost my capacity. If I did that route, I'd have a cab control to pump gas into the factory tank and fill that tank separately. I haven't figured out the spare situation yet anyways, the 37" tires won't nearly fit in the factory area so that is available space now regardless.

 

Maybe consider a universal type fuel cell used in race cars. Move the spare tire to a rear swing away mount and that area could hold a decent size fuel cell.

Sample Fuel Call

 

48 gallon is limited to Crew Cab Long Box trucks; the OP's Supercab cannot be optioned with the 48 gallon tank.

Dave