Check with your DNR to see if they have data on turkeys checked in by each county. That will give you an idea if the potential in your area.
Also check if there's any pasture or ag land bordering the area you hunt and scout the edges for sign.

Walk the fire / access roads and check for tracks and droppings.

Public land birds in heavily pressured places, like MO, are often pretty tight lipped. Small calls and scratching will work better than over calling. MO birds have heard just about every call you could think of throwing at them.

Good luck.