2011 Cascadia with a D60 and no DPF?

Was this a special order truck or maybe a glider configuration? I saw a 2011 Cascadia for sale with the D60 and no DPF. I'm curious if this was a regular option still at that model year or some sort of special order or maybe it was built as a glider?

 

This is a picture of the engine. Just seems strange to me, the truck it's self is pretty plain jane, no side skirts or cab flairs, it's a flat top with the roof wedge instead of a condo. It's a pretty cheap buy though about $25k with a tad under 700k miles.

My issue is I've driven 2 different DD15's and 1 DD13 and they are good motors but I like the idea of no DFP on a used truck and from what I understand the D60 is about as cheap as you get when it comes to rebuilds and parts. I just have no experience with them though.


Then on the flip side there is also a 04 Classic XL near by with a rebuilt D60 (2016 with papers) that has a 13 speed that was just replaced and has a APU on the truck for $24k.. I've only driven Cascadia's though and not sure how I'd like a bigger truck.