Gravity Flow, originally coal fired furnace. Probably converted to gas in the 1960s when gas was piped into towns across Kansas.
The principle is heat rises. So the original thermostat did not require electricity. It just opened and closed dampers.
Large ducts in the basement to the 1st floor. Many times you will see the supply hit a wall and a register on each side. Sometimes a wall cavity to second floor. Sometimes just a supply grill in the ceiling and another directly above it on the floor of the 2nd story. Balloon framing. Where does the heat go?
The returns are usually large floor grills. Many times they are actually made of wood. Large, 20x30 is not uncommon. Beautiful! 2nd Floor return is the stair case. Look for a return on 1st near the bottom of the stair case, and one more. I've run duct blaster tests on two of these. Both were tight, less than 6 CFM per 100 sf of conditioned space. Energy Star standards. You don't have to do that for Efficiency Kansas.
Be careful with the furnace and the ducts. If they have not be dealt with since the conversion to gas, they are probably insulated with Asbestos. UGH! $$$$$$$. The burner, if the size can be found is probably 100K or 125K or 150K. They didn't care back then. I would also wonder about the pilot valve and associated plumbing.
You may have associated coal handling equipment in the basement. If present, probably stored. But look for it. Automatic stoker, coal shovels, coal bin. Coal Delivery Doors in the Foundation Walls.
All sorts of opportunities for mischief and upgrades.
You will have two costs on the replacement furnace. Removal of the monster (with or without asbestos). Then installation of a forced air unit and the new plenums that go along. I doubt you have someone in town to deal with the asbestos, but perhaps. Otherwise Wichita or KC. $$$$ If they remove the basement and crawl ducts, make sure you are ready to spec galvanized and sealed ducts, not the flex or duct board.
Think about the orphaned hot water heater. You will be doing a condensing furnace. The water heater to heat up that old masonry chimney or a new liner for the chimney. Perhaps you can make a condensing DHW work.
Then you have a chimney space to run an actual supply upstairs to second floor for air movement. Comfort issues on 2nd will probably be a big complaint If you can't use the chimney, maybe there is an old dirty laundry chute you can use, or both.
What kind of kneewalls will you have? Be prepared to measure them, and measure them, and measure them.
Infiltration! Is there existing cellulose that has been blown? Maybe not to bad then. If it wasn't done properly, then you will probably need the CRF factor. Be familiar with Krigger and Dorsi on balloon framing upgrade techniques. There will be k&t holes new elect. holes, there will be open places where they pieced top plates. You may well find, boards that have finally dried out in the attic and the shrinkage or warping opened spaces for leakage. Don't forget your original porch roofs for leakage. Be prepared to be drilling a number of holes for your manometer probe or to find a number of cracks or holes large enough to probe.
Check the attic areas that you can. Be prepared for some that you can't get to. Have your drill and plugs ready.
OK, guys and gals! What did I miss?
Bud, Trayce probably did not cut her auditing teeth on these types.