3.6 Pentastar?

I just did some research on these and there has been issues but if you get newer that 2016 you will get the PUG, Pentastar Upgrade.
I would buy a new one but since you said Gladiator it would be the latest and greatest. I think there were upgrades after the PUG. Here's a great article on the upgraded version. Biggest thing was the EGR cooler. That was the source of most of the hate for early Pentastars.

PUG — the Pentastar V6 engine upgrade