What you are looking at here is the hot and cold coming up in the rear with a ball valve shut off, next the cold dives into the tank but also splits off to feed the Thermostatic Mixing (tempering) Valve. Tempering valves are important when installing wood-fired and solar loops (which can get up to 212 degrees) because they protect against scalding temperatures at the tap. This is a serious concern, do not install a solar or wood-fired system without one.
The hot water comes up as per normal, before feeding the mixing valve, and I like to throw a temperature gauge in here just so I can keep track of what's going on in the tank. A street female fitting adapter is not something you'll find at the normal hardware store, but is excellent for keeping things compact. The pressure gauge (top right) is not strictly necessary, but I like to have one because pumped systems are closed loops and without much plumbing to dissipate excess pressure, this will let me know if I need to add an expansion tank. On that note, I'm also planning on heading back and throwing in a brass check-valve just downstream from the pump to keep high pressures from back-feeding into the weak vinyl hose and nylon fitting.
Protruding out the right side of the tank is the Temperature Pressure Relief Valve, which spills extra pressure and hot water when the temperatures get too high. Generally in solar loops we replace this with a simple PRV valve to allow for higher temperatures. I'm lazy so I might not. The PRV feeds a pipe which exits below the trailer, also very important.
In the front is two capped off T's, these will feed the thermosiphon wood-fired hot water loop on one side, and the pumped solar hot water loop on the other. Finally I painted the whole thing to keep it from looking stupid in it's exposed location.