The Buyers Products Van Ladder Rack # 3371501310-3 fits on vans that have a gutter design on their roof. According to my research your 2015 Chevy City Express has specific points on the roof that are used to install a roof rack.
Since this is the case I recommend installing the Yakima CoreBar roof rack which uses the following parts
60" CoreBar Bars - # Y00422
SkyLine Towers - # Y53TR
Landing Pad 22 - # Y00248
One of the nice things about this roof rack is that you can remove the crossbar... view full answer...
Thanks for the pictures! The switch didn't get added to the item # PD4060K until 2020. It looks like from your pictures yours does not have it. If this is the original converter that came with your 2018 Forest River that explains why it's not there.
You would need to upgrade your converter with the Replacement Converter Section for Progressive Dynamics 4000 Series RV Power Control Center item # PD4060CSV which will have the updated switch.
I have linked a picture below that will show... view full answer...
The Vortex Aero crossbars item # RRVA165B-2 do fit your 2015 Chevy Express Van. You will need a couple more components to add a roof rack though. For this you will want the Chevrolet Express Van Roof Rack by Rhino Rack. This system has a 220 lbs capacity and mounts to your roof without drilling. This roof rack includes the following parts:
Rhino-Rack Vortex Aero Crossbars - Aluminum - Black - 65" Long - Qty 2 item # RRVA165B-2. These are the ones you referenced.
Rhino-Rack Roof Rack... view full answer...