I bought a Hunter Non Programmable that looks about like this at Walmart.
The left panel is hinged for switches, and the right is hinged for 02 - AA Batteries. Mine isn't quite the same because the one I pictured has a "Filter Change Alert" and apparently 03 temperature modes.
On mine, the wall thermostat controlled Furnace ONLY and there were only 02 wires coming out of the wall and connected to the OEM thermostat. If you have a wall thermostat for your A/C, I can offer that I haven't tried to use one of these to control both, BUT others have, successfully, in several cases. I think somebody could post a link to such a project. If you're not controlling A/C as well as Furnace, just connect 02 wires and go.
We use the furnace only rarely, but I really like the conversion when we do.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB