I can't say much about the fitting other than that is not factory, someone modded something along the line. That is a fairly generic filter head however.
I have also added a Goldenrod housing on my Diplomat, but rather than using the Goldenrod filter as shown, I selected a "screen" element filter to act as my pre-filter for everything approaching my FASS pump. I didn't want to restrict the flow too much, but did want to trap anything large enough to be easily visible that might be coming out of my tank. I'm STILL dealing with large quantities of some kind of flaky brown stuff (not rust) coming from the tank. I catch around a couple tablespoons of the stuff for every 100 gallons consumed.
As for using the goldenrod on a stationary system versus an RV.... Not much difference in the application, it is a housing and a filter, processing what passes through it. It doesn't care whether it is moving or not.
03 40' Monaco Diplomat: 1020 watts solar, Victron inverter. FASS, TRW steering, 23 cuft Frigidaire, D/W, W/D, Magneshade, Wood Floor, New cabinets, diesel heater