This is similar in design to the one I built for my G, thought mine attaches to the body rather than the frame. 

Mine holds 10 gallons and is also filled/drained by a pump.  In practice, if I start with the extended range tamk empty and the main tank nearly so, both fill at about the same time.  This is using a "car diesel" nozzle, as opposed to the giant truck nozzles.

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I bought a bi-directional vane pump off of eBay for cheap.  Works great.  It is mounted with hose clamps onto the same feature that Front Runner uses.  Given noise transmitted by the direct-to-body mounting, you cannot miss the fact that the pump is running.  Also the sound of the pump running dry is easy to detect.  The pump isn't supposed to run dry for very long.  For short periods, diesel is a nice lubricant.

For the breather, I T-ed into the factory breather hose at the highest point up by the fuel filler.   That way I know it is full when fuel starts spitting out of the breather vent that is visible a few cm down the filler on the left side. 

Their filling system is actually pretty clever.  Much easier than what I did.  Instead, I pulled the tank sender and re-purposed the secondary fuel pipe that is normally feeding the park heater.  After using this for a while, I found that the narrow pipe filled too slowly.  I have since rebuilt the sender with a larger pipe made from malleable copper.  This moves a lot of fuel. 

I used clear braid reinforced hose, which was great for diagnosing initial problems.  Dirt and flying debris has rendered the hoses more translucent than clear, so the diagnosis benefit is gone now.

One final thing.  Since both ends of the fill system are dip tubes submerged into fuel tanks, there is a possibility of siphoning from the higher tank level to the lower.  To prevent this, there is a tiny (dental drill) vacuum breaker hole at the very top of the dip tube in the extended range tank.  This results in air bubbles being sucked in with the fuel when transferring back from the extended range tank.   This probably slows it down a bit, but hasn't really been noticeable.

The drawing below was my initial starting point.

The picture of the pump has the vent line in a misleading position.   I don't think it had been connected up yet.

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It should work with any fuel.  The design doesn't meddle with the venting system in any substantial way.  In theory, the various nanny systems won't know or care about it.  The impeller of the vane pump needs to be 100% compatible with whatever fuel you plan on using.  Gasoline is a strong solvent and a lousy lubricant, so that may be a challenge.