shakey,
I don't think Dodge put out a dual tank setup since the early 80s. I was going to do it on my Crew Cab and had some of the parts. I was going to use a EFI fuel tank/brackets out of a 1988 to 93 Ram charger and use a matching fuel send unit from a Dodge diesel in the ramcharger tank, then have a electric valve (get at any auto parts store) to switch tanks and use a double pole, double throw switch to change tanks and sending units so I get fuel readings off the tank I was using at the time. The hardest part of this for me was to have some one add a fuel door to the side of the truck. I gave up the idea because I would loose my spare tire location. I do believe that there are companies that make an aftermarket larger main tank for 1st and 2nd gen trucks, but I hear they are very pricey.