I agree with quickcrx702. Get a buckling spring keyboard from Unicomp. You're getting a brand new keyboard, set up just the way you want.
Buying Model M keyboards almost always involves tinkering. Maybe it's had some keycaps replaced and they don't match. Maybe it has one or two keys which are wonky. Do you want to do the screw mod?
The point I'm trying to make is that while you're tinkering with your 20 year old Model M, your Unicomp keyboard will be right there as a daily driver, working just fine, and with a Windows key, too.