Replaced my 2866 springs with 2864 springs purchased from @cruiseroutfit . I went from 20.75" or so in the rear to 23.25". I upped the front to 21.25" from about 20". That was as far as I felt comfortable cranking the front while maintaining sufficient droop.
I think the 2866 springs were just compressed too much with the weight of my bumper/fridge etc. I was expecting the ride to be really rough with the 864, but honestly I think it's actually driving a bit smoother with the heavier springs - certainly not any stiffer than it was before.
The 864 made sense to me over the 863 in part because everybody treats the 860/865 as a "medium" spring. If you look at the specs, the 863 is only 30# heavier. That just didn't seem like it would be enough for me.
My only "complaint" is that OME uses different length driver/passenger side springs with the 864. I suspect that's due to the 80-series application. I don't think it's really needed on the 100-series and has introduced about 3/8" lean. It's not too noticeable though so I'm going to drive it for a few thousand miles and then assess if I want to install a small spacer on the passenger side.