Here's a pic of the heater hose hookups on the engine. The top is the "T" fitting (supplied) with the temp sender screwed into the back. Originally the temp sender screwed directly into the thermostat housing (behind the white washer). The heater output hose goes off the top of the "T" fitting.
The bottom of the pic is the return line ("T" fitting with blue hose clamps..supplied) The return hose from the heater comes in here.
Both hoses go from the cab under and behind the left rear motor mount, over the drive line/power steering lines, under the oil pan and up in front of the right front motor mount. The return line goes from there directly to the "T" fitting. The output line goes up and over the air filter intake horn.
The OEM thermostat is 160f. This is for the x595, 455, 4110 & 2210....no other options. You need a 195f thermostat. The 160 puts out luke warm air and won't allow the oil to reach high enough temps to burn off acids and keep from building sludge....well..maybe in Texas..but not in Alaska. I believe the engine also will burn fuel cleaner at the warmer temps.
Shucks Auto has generic thermostats in sizes (diameters). The 2210..etc..takes a 44MM thermostat and they have them in 2 heat ranges...180 & 195. The 195 allows the cab heater to really put the heat out...shirt sleeve operation.