Uniforms:
A lot of what was used in the Korean War was WWII surplus - uniforms and gear issued from inventory, just as we do today.
Suggestion on kit sources:
At The Front
What Price Glory
WW II Impressions
I've used all of these for living history uniform and gear impressions and events.
The first COA is to research who he wants to portray, the unit, if there's a specific individual, time period and then dig into the culture, current events of the period, and everything related.
Your jeep has unit markings so an obvious starting place would be that unit. Also, as you may already know and Wes has pointed out, M38s weren't used in the Korean War, at least not until the very end and then not in many numbers. So you would likely want to do a stateside or EUCOM impression.
These are all purely suggestions to help guide what you want to do. As someone noted, though, you're in front of the public and, in their eyes, become that person and period so become as knowledgeable as possible on the period and impression you're representing. Otherwise go in 21st Century civvies.
If you have questions I'm happy to answer any. Grab some of the history books on the Korean War and the period before/after, especially any picture books to aid in your research and display.
Have fun and always look for ways to improve. Your jeep clearly shows your attention to detail. It's a beautiful ride!
