I used a pair of spare tire winches off of the late nineties Dodge trucks. The quick key is enough to raise and lower them. A simple angle iron bracket bolts them to the frame. I ran the same winches below my side bars on my last truck. Probably a dozen years all together now. Works pretty well. Spreads the load when lifting the rear with the exhaust jack too... I do like that idea of the sand rails to protect the tank though.
That's why I'm scratching my head why I haven't heard of this kind of mod before. I'll be taking some measurements this evening on the Woofwagon to see if this is possible. I'm thinking that a 6 position switch/valve would be able to handle 3 tanks. The biggest issue would be to wire up the three separate fuel level floats to the gas gauge.
The main thing I'm noodling over is how to I would connect the tanks together. My initial though is to use gravity or some sort of siphon with one way check valves for the auxiliary tanks to feed to the stock tank. Fill all two or three up and when the main tank starts to drain then the gas gauge starts to drop. I have a gravity feed system for my 100 gallon tank on my Powerstroke and it works great because there is a float/check valve that keeps the main tank below it topped up until the 100 gallon tank drains. I'd like to remove the requirement of using transfer pumps if I have to.
As long as you have both a fuel transfer line and a vent line connecting both tanks, then they should simply act as a single tank without pumping (provided they are at the same level)
If they end up at different elevations, then pumping would be required.
The fuel connecting line (at the lowest point of both tanks) would have to be a fairly large diameter to accommodate the higher flow rate of refueling.