problem is the amount of trucks you can make... 1500, 2500, 3500, reg cab, quad cab, crew cab, short box, long box, 4x2, 4x4. there is just the truck configurations... then add 3.0, 3.6, 5.7, 6 speed, 8 speed on light duty and 5.7, 6.4, 6.7, manual, auto, aisin for drivetrains... and we haven't even touched the hard stuff with packages and options. mathematically, it's over 300000 light duty trucks i can make.
so that is why the websites suck.
on to your question!
the diesel is available on all trims except SXT and sport. the ST model you technically have to go for a "tradesman" which is an ST with a hitch and a spray in bedliner.
getting one is a whole different story though. i have an ecodiesel on my lot for about 45500 right now... slt with a bunch of wacky options (ram box, rubber floor, but 8.4 touchscreen...?) i tried to find a cheaper one out there and couldn't. 2018's can't be ordered, so you are stuck with what is already ordered/out there in a 2017... and yep, 17's are still showing up.