engineer bob, what's the serial number? Many of us are talking about 1978-sh, but the SN on the BB should give a good indication. There are some anomalies, but without full paint and markings and OEM parts, its hard to draw conclusions on the year without the SN.

Vintage Trek Bikes- Information on Steel Road Bicycles made by the Trek Bicycle Corporation, bike has a really good serial number directory.

Trek tweaked the geometries gently going from the '70s through the mid-80s. It's not clear the old engineer's drawing is applicable beyond its year.