So for venting, the F-150 tank has a single vent tube at the top center with a rollover check valve. Now I only have the single F-150 tank so mine is gonna be a tad simpler than a dual tank setup. But I just connected the vent line to the stock EVAP line. Now I don’t see any reason why you couldn’t connect both tanks to the same EVAP vent line via a T fitting. As long as both gas caps are working properly, I don’t see why it would throw any codes or cause issues with the EVAP system. Also if you want to simplify things even more and not deal with the Charcoal Canister possibly failing early, you can just ditch the canister and run the lines straight to the vapor purge valve. I did that a few months ago with no issues. I don’t think I’ve even thrown any EVAP codes besides system rich code every once in a while (I guess I have thrown EVAP codes then, huh?). Anyways, I think if you are trying to keep things as simple as possible, you could possibly just let both pumps run concurrently at all times (probably not the best option since if one gets less return flow than the other, it will drain one tank faster, therefore burning up a pump prematurely). Another simple option is to put a set of switches on the pressure and return lines, then a selector switch for whatever tank you want to pump from. This would just be a PITA since you would have to get out and manually switch the pressure and return line valves. Last option I can think of is just use on of the Ford, or Chevy selector valves and figure out how to let that do all the work. I’d think having two fuel gauges would be way more simple and much more accurate since the gauges work on a totally different ohms spectrums, while also reading in opposing directions on the spectrum. I couldn’t figure how to make the stock gauge even work for the ford sending unit. One uses 2 wires while the other uses 3. There might be a way to make it work but I couldn’t figure it out...