Here are a few. Things you may want to think about.
- how many long guns should it hold?
- are any of them scoped?
- do any require additional width (long bolts)?
- did you want the rack to provide some level of security?
None are two piece design, but an adequate bearing surface could negate the vertical stiles.
These are some of the design criteria. Pehaps I could work with you and any volunteers in providing a dimensioned drawing for you, if nothing can be found
Materials depend somewhat on your tools availaility.