Is it the oven burner that won't shut off, or a pilot light that won't shut off?
If it's the pilot, there should be a small screw either behind the oven knob or on the pilot itself to shut it off.
If it's the oven burner, I can't answer your question other than to say you need to find out why it's still getting gas if the oven knob/valve is shut off. The 50+ year old control valve is very likely the culprit. Depending on how mechanically skilled you are, you might be able to rebuild it. If you restored the camper yourself, I suspect you have the skill.
curmudgeon: noun; a crusty, ill-tempered, irascible, cantankerous old person . . . .
79 27' Holiday Rambler Statesman, 78 32' HR Imperial, 85 36' HR Imperial 5th Wheel