I finally (re)found my copy of "How to Build A Working Digital Computer" by
Alcosser, et al, published in 1967. This is the "paper clips and spools"
computer - definitely worth a look -
http://www.sideslip.net/digital_compu/
. It's a scan of a copy from a dying book so parts of it are not too pretty
but I think its all there.
Enjoy -
Jack