OK, I've decided on the design of the e-bike I want, and I will be building it. The motor is in route to my home and I obtained a free 10-speed today. Progress!
Free Murray "Explorer" 24" 10-speed (24" is the right size for me):
The frame fresh from the Goo-Gone treatment (fingernails, Goo-Gone, elbow grease, and an old sock):
The Bosch 24V 350W DC permanent magnet motor on the way (old but unused - $20 with shipping on ebay):
Here are links to the design:
http://autospeed.com/cms/A_2419/article.html
http://autospeed.com/cms/A_2421/article.html
http://autospeed.com/cms/A_2430/article.html