Natural gas is just different than LP; not as dense, lower BTU/lb, but a better value (dollars per BTU).
The decision to go to NG or LP for space heating is generally based on the availability of the local NG utiliity.
NG's advantages are lower operating cost, if the utility is available, and more continuous service.
LP's advantages are portability, and possibly lower installation cost, since NG has to be piped from the utility to the appliance, and LP can have a short run to the tank.
If sorghum cooking is a only a few hours a year, I'd think LP is the best value.
I'd start collecting used natural gas burner assemblies over the next year, buy LP kits for them and work far away from the house.