I have seen a lot of engines usually the 4.6 and 5.4 ford engines on construction vehicles in the 400,000 mile range some of these companies keep their trucks for 15-20 years and actually rebuild them and repaint them when they get run down but the engines last a long long time. The 4.0 Toyota is a good engine.
That's funny. The shop truck was a F-250 with the 4.6, and regularly serviced by our two full-time mechanics, and the owner is a believer in buying the recommended or premium fluids and filters (Amsol synthetics, Yamaha OEM, Motorcraft, etc). This particular truck, purchased new from the dealer, had Amsol Oil at regular Severe Service intervals (time or miles, whatever came first).
Motor blew on the highway pulling an empty horse trailer at 140,000 km (87,000 miles), out of warranty due to age. The only 4.6 we ever had, so no idea if that's bad luck or perfectly normal.
We replaced it with another Ford MY 2014; the owner is a lifetime "Ford Guy".
My experience with the Ford gas V8 engines is they really perform poorly, hard (or no) starting, long warmup loop, poorest fuel consumption, when used in a cold weather environment compared to the competition (RAM. GM, and full size Toyota). They seem OK if the mercury stays above freezing (although our engine failure incident was in July).
Below around -25F they really stand out vs other light and medium duty trucks, and not in a good way.
Does your V6 have that annoying "Toyota Tick," or is it still quiet?
We have a Prado with the 1GR-FE, just 70,000km, about 44K miles. That thing, despite regular servicing and long highway runs, ticks noticeably. Almost like a push-rod or solid-lifter sound you might get from older vehicles when running normally. 
