Gas to propane conversion in old stove
Depending on how the gas valve or the burners are designed it may be possible to convert to propane fuel. Most conversions are as simple as changing the burner orifices. The orifice is the component that has a miniscule opening that emits the gas just before it ignites. The size of the orifice opening is dependent on the gas being used and how many Btu's are required. Natural gas will have a different sized orifice than propane. One Should not be used with the other.  Look around the gas lines for a small spud like this orifice spud. Some spuds come with no openings and can be drilled to a custom opening.