UPS is a pretty unique customer.
With regards to the LS vs. Cummins comparison, longevity and reliability is HUGE for UPS. They keep their trucks a long time, a lot longer than other delivery users. And every time a truck is down or needs repair it's a massive cost to them when you factor in the resources they need to replace that truck for however long its down. So for them that kind of thing is very important.
That said, I doubt you'll see an engine that large, Cummins, Ford, or otherwise in upcoming orders. They actually don't use a ton of power (or rather have figured out they don't need more.) They've experimented a lot with downsized engines to great results. But more realistically you're going to see a lot of electric for them. They're actually a much better candidate than a lot of others given their light duty cycle, light GVW, and the fact their vans return to base every night.
But that's just the step van part of their business. It's going to be awhile before the rest of their equipment transitions away from diesel/natural gas.
