So I did a little more searching, and here are the motherboard capacitors used in a 128k:

33µF 16V, 2 pieces

4.7µF 35V, 1 piece

Got that info from here: http://retromaccast.ning.com/profiles/blogs/compact-mac-analog-board

He also lists the analog board components, which I found some other, older info on here: http://macfaq.org/plusanalogue.html and here: http://www.jagshouse.com/vertical.html

What are folks' opinions on doing pre-emptive replacement work on the analog board?