I have always drooled over the 870 but never gave thought to an install as I assumed it was too big to fit reasonably.
I've also been struggling to decide which new TM to get to replace my tired, worn, and long ready to retire unit.
On a whim I printed out the dimensional spec sheet for the 870 and headed over to Nissan, it turns out it will fit perfectly in a 2500 with a waterpond reel. The reel fits behind the partition out the side door, the waste tank tucks in between the pond and the wheel wells (like they designed it to fit), and with the 870 rear facing against the p/s ww it leaves three feet open to the d/s wall all the way from the rear door to the waste tank....plenty of room.
I've had to hunt but managed to find a couple of pics of an 870 tucked into an Econoline, but that's it.
https://www.facebook.com/media/set/?set=a.741693015847932.1073741842.283035788380326&type=3
I'm not sure why these vendors & installers don't take more pix of their work as it would help with decisions for sure, here I dismissed the idea of getting one of SS most expensive units. A few install pix on SS website or posted via the installer could make an easy upsell for them.
As for the 870, I can run it on low/med for most residential to save fuel when I work by myself and have all I need on the truck, then use a trailer with a second/third reel for 2.5" hose, longer commercial, dual wand with a monkey, my monster fans, etc. I could also stock the trailer with water recovery equipment as it's something I've always turned down due to not having a quality/capable TM. That way the trailer stays home most of the time and only comes out for 'big' stuff. I don't 'need' an 870 for residential, not by a long shot (or the $10k price diff). But having the option to stop turning down jobs and maybe even start marketing for big stuff and water recovery might make it worthwhile. That or someone will get a great deal on a gently used 870 in 5-10 years :-)
Scott, I too would love to know the real world fuel GPH on the 870s three speed settings.