Mate, I have been living with this problem now for 68,000Km
I have become used to it.
Most vehicles on the market have temperature gauges made for the owner. (No movement unless the car boils). Chrysler have fitted graduation gauges, just like the old mechanical ones that give a true reading.
Our van weighs close on 3 tonne, we tow it at 90 to 100kph, depending on the external temperature. Queensland is quite hot so most times it is 28 to 40 deg C outside.
I only worry about the transmission oil temperature, not the engine any more. The motor will cool as quickly as it heats up and given that, I don't see a real problem. I just back off if the needle is about to hit the top mark, and it works.
The tranny is a different story, I drive by the temp on the readout. I try to keep the auto in between the 96 to 98. Some times it gets to 100 for a brief period, so I slow down.
Both the engine and the transmission will withstand a lot of heat, hence the expensive oils used. We have not long finished a 12 month caravan trip around Australia, 32,000 km. Only trouble was the tailshaft. Rear uni joint ran out of greese and became "untidy". Jeep replaced the whole shaft under warranty.
Other than that, not a hiccup. Serviced every 10,000km and all was well.
Temp of the engine and transmission remained constant, even in 40 deg C.