There is a mail-order bike shop outside of San Francisco that has links to homebuilder plans for bikes and trikes. Try
www.gaerlan.com. they sell components and parts for homebuilders as does
www.poweroncycling.com in Florida. Look in the upper left hand corner of the Gaerlan home page for the builder link. You might also look at the messageboard on
www.bentrideronline.com. There is a section on homebuilds there too.