I use those two sites as well - but then often find conflicting info when going to other sites to actually purchase. For instance...
I'm looking for the rear Jounce Bumpers (bump stops).
When I search the AC Delco parts catalog it returns just one part - Part# 15200997, it also says POLICE PKG(Z56).
When I search GM Parts Direct it produces several results with this one GM (15115208) indicating ZW7 - which is what I have.
Most retail sites say it's the correct part, but a couple say it's not. Very frustrating.
Don't waste your money on Monroe loaded struts......I think you'll be disappointed. I did a bunch of research when replacing my 2008 yukon struts. I settled on 2019 tahoe take-offs from an auto recycler. 2007-2020 all have the same mounts for front struts.
I compared my 2017 to my 2008 and they were identical in measurements, so I pulled the trigger and got a set of rust free, 19k mile OEM struts for $350 delivered. They bolted right in and ride great.
I wouldn't worry about the RPO codes too much since you don't have the auto-ride system. Just find something similar to what you have, or use their description of the code when they list them. Some are normal ride, others are a heavier duty rating for suburban, z-71 package, etc
Ebay.com
Car-parts.com