a hybrid would be a great idea. Does Ford have a current hybrid powertrain in the 150 -300 ftlbf arena ? (I dont know)
I have no problem with any of the above solutions. I dont work for the USPS, but I do get mail from them so I'd like their fleet to be as efficient as possible, and Id happily trade some efficiency for ease of maintenance or relaibility (the old mail truck, LLV, had a GM-sourced 4 cylinder that had already been in production for a number of years.
I'm just mostly surprised that this much decision-making was made without such a detail already locked down. the USPS chose its truck, but the submission didnt state (or know) what kind of engine it'll run. Thats not a dealbreaker for a fleet the size and scale of the USPS, but I would think that its a big one. What if Oshkosh started shipping this trucks with Ford 5.4 V8s in them ? or the 6.0 powerstroke Diesel ? or anything designed and build by Chrysler

the mail would never get here
Thats an exaggeration and a joke, and again, this decision doesn't affect me really at all, but as a car guy, I'm curious what engine we are going to get *thousands* more copies of.
(UPS trucks are mostly proprietary, and other shipping companies are flooding the Used market with Sprinters, Metris', Caravans, NV200s, Promasters and Transits.)