Welcome to BYC! Glad to have you join us!
When I started out I also was looking for Wichita plans that I could use to adapt and contacted them. It took a while but they did reply. They told me they didn't have plans per se or a step by step guide, but a sketchup file and a materials list.
Unfortunately (or fortunately?) they emailed me after I needed my coop figured out so I'd already drawn up my own plans in sketchup and started construction by then.
If you're at all handy and can draw a little, you can do it too. It's a pretty simple process. What really helped was watching other people on youtube build similar coops. That showed me what I wanted to keep and what I wanted to change in my own design. I made mine to accommodate deep litter in both coop and run, added built in storage, put the access doors on the shorter end instead of the longer side and increased the footprint to 8' x 10'.