I just completed a local trade with macg4: he got a carload of 680x0's and early PPCs, a couple of monitors and my spare IIe. I got a Mac Plus and a whole lot more free space in my basement. All in all, a pretty fair trade. 
One small glitch: macg4 didn't have a spare keyboard or mouse. I found a mouse on eBay, but I have a moral dilemma about paying over $50 for a keyboard. I did a little research, and found that both the 128/512/Plus keyboard and ADB use four pins, and the same voltage.
128/512/Plus keyboard:
Pin 1: ground
Pin 2: kbd1
Pin 3: kbd2
Pin 4: +5V DC
ADB keyboard:
Pin 1: ADB
Pin 2: power switch
Pin 3: +5V DC
Pin 4: ground
Detailed pinouts available at http://pinouts.ru: search for "macintosh keyboard"
I also happen to know that an S-video cable is wired identically to an ADB cable, so I won't have to cut a perfectly good ADB cable. I could instead use an ADB Keyboard II or Extended Keyboard II (neither of which has a permanent cable, just 2 ADB jacks), plug an S-video cable into it, lop off the other end of the cable and crimp an RJ13 plug onto it.
Will theis work? Am I at risk of harming my Plus? Or am I a the mercy of the scalliwags at eBay?
Nope, won't work. The protocols sent over the wire are different. To put it simply the Plus keyboard speaks German and the ADB one Chinese.
I can't believe the keyboards are on eBay for $50. I bought one at a local store for $10.
I'll make you a deal. I need a set of system disks for my Mac 512K and none of my computers have a floppy drive. Let alone one that can write 400K disks. I'll send you a keyboard if you'll send me a set of system disks.
I sent you a PM.