I grew up in Saline County
I found some three-ringers once, where Fouche Creek crosses Highway 5, in Pulaski County. I believe there was a camp there because all I found were drops.
I read where Union troops camped down by the old steel bridge on the Saline River. Undergrowth keeps a detectorist from penetrating the tangles. It's at the end of River street, in Benton. I don't know which side they camped on.
At Collegeville there are several Civil War soldiers buried in the cemetary behind the old church.
The old campground at Salem would be a fun hunt. I gave it a cursory visit 20 years ago but didn't look too hard at the time.
Go to the history room at the Saline County Library, if you have not already. Also, if you have not been to the Burger King on Military Road, you need to go. Lined on the walls are huge prints of Benton from the late 1800's to the mid-forties. It will be of some interest to you, I'm sure. I now live in Pearcy (just west of Hot Springs) and seldom get back to Saline County. So have a ball.
Happy Hunting.
aj