Hi Stan,
I agree it a grease fittinhg on the wiper shaft would make a great preventative maintenance step. I don't know if the shaft housing is thick enough to drill a hole and tap for a zerk fitting. Even if this did happen it would be difficult, but not impossible, to get the the drivers side fitting. I'll see what i can come uop with and advise. While I had the dash apart I'm taking the working heater core out for service. I'll let you know what the shop recommends.
Jeff C.
1970 280SL 4-speed