The RV Water Filter Store sells the aforementioned Watts 263A in five different "flavors". All of them have the same 263A regulator, but, as the price goes up on the various models, so do the options you get.
1) You can get the 263A stripped...just the regulator
2) You can get the 263A with a low priced gauge
3) You can get the 263A with a low priced gauge and the SS hardware
4) You can get the 263A with a higher priced SS oil filled gauge without the SS hardware
5) And then the Top-of-the-Line 263A with the higher priced SS oil filled gauge and the SS hardware kit
The stainless steel parts will reduce corrosion (won't stop it completely; dissimilar metals are going to corrode, but, SS makes it a "long term" process), the oil filled gauge is a more professional and reliable gauge and will give you better, consistent readings.
Any of the 263A units are great, but, I've never figured out why you would want one without any gauge, but, they offer it that way. I've got the "Top-of-the-Line" unit and have had it for years. No corrosion, very consistent readings, no leaks and I've never had to do any maintenance aside from replacing the intake screen every couple of years (I could clean them, but, you can get a 10 pack of the things at the hardware store for a couple of bucks...)
Somebody asked about "set-up".... Put the regulator on the spigot at the pedestal; everything hangs off of it. I knew a guy one time, a newbie, years ago, that put it at the trailer and ran his hose up to it (wanted to protect the trailer, right?). He went away for just a couple of hours and didn't turn his water off (only a couple of hours; actually about an hour and a half) only to come back to his hose blown off the pedestal connection with water merrily flowing all over the ground... Yes, I was embarrassed, learned my lesson well. Had to go buy a new hose, stand in the lake to put the regulator on the pedestal and then the hose... Put the regulator on the pedestal and protect all of your water equipment