Hey guys, how about some help. I tried to buy a much advertised repro heater control for my 68, only to be told it is promised but not available yet. So I bought a faceplate and replacement defroster lever and I'll fix up the old one. HOW DO YOU GET THE D____ knobs off! The levers are a little rusty, and the knobs are stuck tight! I'm afraid to pull too hard, don't want to break the levers.