The advantages of a gravity
furnace go beyond retro style. Since they use no
electrical power at all, they are ideal for boon docking. While the gas valve can be replaced, the valves that are available are expensive, and have a different port arraignment. This means that some tube bending will be required to install it.
Duo-Therm Furnace Gas Valve, Replacement 710-201MC
https://www.supplyhouse.com/Robertsh...w-18-Capillary
https://www.walmart.com/ip/710-201-Gas-Valve/50501892
Hey look at that! Walmart sells it.
My preferred option is to locate the exact same valve, on kijiji, in some other furnace of the same vintage. I see that you are in Alberta, me too. I just did a quick scan and only came up with one contender:
https://www.kijiji.ca/v-trailer-part...ationFlag=true
He wants $200 for it, but I have seen them for as low as $50. Of course, the gas valve may not work, but
Randy Bishop tells me that he has never come across one that a bit of cleaning would not fix.
That brings me to my next point. The thermocouple is a part that can still be purchased.
https://www.amazon.com/Robertshaw-19.../dp/B001TXJ06M
Bring yours to a furnace service shop. They will likely have one you can use.