[RidingRoadsAndTrails]

I don't have first-hand knowledge on the new option, but here is my guess based on installing a heater on my 2021. Prior to this option, the auxiliary fuel port is on top of the fuel pump and dropping the tank is the only way to access it to connect your fuel line to it. See the black/yellow bit in the pic below. They will be providing the elbow connector and a fuel line of some sort to connect to. Sprinters have had this as standard equipment for some time.

However, if you ever plan to use your gas heater at an elevation above about 6000ft, cavitation can be a problem and your heater may not work reliably. Espar provides a different standpipe to mitigate this problem. Their standpipe is considerably thinner than the standard pickup line. Compare the diameter of the orange line to the stainless steel line in the pic below. Search the forum for "cavitation + standpipe" for more background on the issue.

So, by Ford making the access to the aux line easier to access, you still may not want to use it unless they also made it thinner.

BTW, the day I dropped the tank and installed the standpipe stands out in my mind as the most difficult day of my entire build, even though the end result was good.

 

[RidingRoadsAndTrails]

First, I need to do some more research on the altitude and cavitation issue. My main question is, how effective is the automatic altitude adjustment feature on the Espar M2? Is it ineffective and still requires the alternative standpipe?

I believe you are merging 2 issues; fuel delivery and combustion.
- The automatic altitude adjustment manages the fuel & air mixture to be richer or leaner based on the availability of oxygen in the air.
- Cavitation comes into play with fuel delivery since the heater's fuel pump has to pull fuel creating negative pressure in the line instead of pushing the fuel into the line as the standard vehicle fuel pump does.

I have the Espar M2-B4L installed with the Espar standpipe. I have tested only as high as 9000ft but so far have had no issues.

 

[RidingRoadsAndTrails]

If I can persuade my local garage (friendly folks, have known them for years, not the dealership) to drop the petroleum tank and install a line for me, should I do that? I’m not yet set in my plans for heating, but dropping the tank myself seems hard and makes a dedicated small (diesel) tank seem a lot more attractive.

My opinion (obviously, since I went that route) would be to install the standpipe into the existing fuel tank. A second tank and having two different fuels seems like long-term pain. My first time doing it took about 16 hours, because I had never done anything like that before and I had to improvise on some of the required tools that I did not have. I'd guess that it could be a 2 - 3 hour job if I were to do it again.