Check out this offering from Charlie Rodgers .. nice writeup and some great accompanying photos!

Courtesy of Charlie Rodgers .. in Office 2007/2010 version of Excel format (.xslx).

The Begginings of a Stanley #4 in Solidworks 2007. There is also an Edrawings model (viewable by anyone with edrawings, a free download for solidworks.com). Still need sht efrog and associated screws, along with the lever cap, but it is a start.

Trebuchet plans in AutoCAD and Edrawings. Based on plans from Dec. 1997 American Woodworker article.