I have not followed the 15AC market for years & don't know what they go
for now days.

Another search thought is to check the condition and type of fuel
tanks. They had fuel cells originally & I don't know the replacement
situation. We put in new cells 38 years ago for a measly $250 each,
which would mean about $2500 each now.

I understood some put in metal tanks as the fuel cells were no longer
available.