Thanks!
Brownsville Marine (current owners of the Hillman site) have nothing. They suggested that I contact Trinity, who purchased Hillman in the 80's... no word back from them yet. I may also have a lead on Mr. Basci, who may be with Trinity now?
Perhaps the Monongahela Transportation museum has something, no word back yet.
I'm thinking the best bet will be to appeal to historically minded folk at a current boat owner, such as Amherst-Madison (who own Drema Woods and Charleston). I'm sure those drawings will exist on board or in the main offices... but I've no contacts there, can only cold-call their info line...

Pat M.