Remember USPS provides universal service. How do you sustain an electric fleet everywhere in the US in 2024?
If the postal service was run by a normal board and we had a less insane political environment, we’d build charging infrastructure to make to make it work. Alas, we live in this timeline.
It shouldn't be too big of a deal to have an ice and an ev share a truck style vehicle, because there's going to be structural support for batteries and probably room for them too; possibly requiring a higher load floor, but depends on design, I guess. Sounds like the target EV range is 70 mi, so the battery pack won't be super large.
Ford makes the F-150 in ice, hybrid, phev, and full ev, I think.