If you can't find anything, the great Ron Tonkin was absorbing Portland area dealer operations around this time period which Ed Rendell may well have been one of?
Excellent article about Tonkin's auto exploits here, a very Max Hoffman like guy on the cusp of importing future best selling offshore vehicle brands into N. America including Hondas/Toyotas/Ferraris/Saabs etc.
http://www.fundinguniverse.com/compa...mpany-history/
Good luck w/ your research and congrats on a very cool Z-28...the CB paint puts it over the top!
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~ Pete