Hey Matt,
Whatever you do, I definitely would not mount it inside the cab. While you might be able to smell diesel fumes, the unit doesn't smell much at all once it's warmed up and burning cleanly. CO is colorless and odorless. Plus you won't notice anything if you leave it running while you're snug in bed in the morning or shopping at the mall. The cab could be filled with fumes by the time you get to the truck. Anyway, all you'd notice is that you had a spltting headache before you keeled over. Don't put it in the cab!
Even if you do install it safely in the cab, if you go and kill yourself by some other means, the investigating attorneys will discover the heater, blame your death on it's being in the cab, and the rest of us won't ever be able to afford one again due to the manufacturer's liability. DON'T INSTALL IT IN THE CAB!!! Oo. Oo.
About the only reason that I can think of for the kit install to be putting the Heater down under the steering column (above the starter and beside the lift pump), is to keep hoses and wiring away from the exhaust manifold. If this can be worked out, and it can, I think just about anywhere else would be easier to get to!
I agree about mounting it too high causing cavitation. The water pump gave out on mine after three years and set me back $150. Don't even think about finding a motor/pump elsewhere, it's custom! You don't want that puppy cavitating!
One of the best installs I heard about was a TDR member out in the great Northwest made a custom bracket to hang it off the passenger battery mount. If I recall correctly it was lower than the battery but still mounted to it somehow.
How hot does it get? The metal side that contains the flame is completely jacketed by coolant, so I'd say it never get's hotter than the coolant itself. It is supposed to shut down if it has an 'overtemp' condition.
All in all, I'm really happy with mine. Someone showed me their brand new Volvo yesterday and I commented on what a nice car they have. Then I walked over to my truck warming itself up.
MTE