A transmissionn oil cooler is always a plus. Heat is the #1 enemy of an automatic and towing generates lots of heat, especially hills (whether up hill or descending with the tranny in a lower gear).
Here's a table showing the life of standard tranmission fluid at various temperatures:
> Temperature Approximate Life of Trans. Fluid
> > 175 F. 100,000 miles
> > 195 F. 50,000 miles
> > 212 F. 25,000 miles
> > 235.F. 12,000 miles
> > 255 F. 6,250 miles
> > 275 F. 3,000 miles
> > 295 F. 1,500 miles
> > 315 F. 750 miles
> > 335 F. 325 miles
> > 355 F. 160 miles
Synthetic tranny fluid holds up much better in heat and is a worthwhile investment for any tow vehicle.
And here's an estimate of transmission life taken from a mid-90's Chevrolet service manual:
Trans Temps vs. Life Expentancy in miles
> > ?Farhenheit = Miles
> > 175? = 100,000
> > 195? = 50,000
> > 220? = 20,000
> > 240? = 10,000 Varnish Starts to Form
> > 260? = 5,000 Seals start to harden
> > 295? = 1,500 Plates start to slip
> > 315? = Seals and Clutches Burn up and Carbon Forms
I don't know of any benefits for an engine oil cooler. In fact, never heard of anybody buying or installing one. For practical purposes, your radiator is an engine oil cooler - it cools the engine block and the oil along with it. I've heard of peole insyalling auxiliary cooling fans for the radiator, though. That's fairly common and it helps reduce the engine temp when climbing hills.
Modern vehicles have variable speed fans and generally don't need aux fans, though they are easy to install, modestly priced and can't hurt. My Workhorse chassis motorhome comes standard with two electric fans in addition to the variable speed, thermostatic clutch, main cooling fan and hey help circulate air through the a/c condensor that sits in front of the radiator.