Dana...if you haven't come across it yet, this below is online from what sounds like someone's '67 'Vette deal w/ a phone number...good luck!.
~ Pete
"...Zone 19 Dealer 423 Status: No longer in Business
Dealer Name Lyman Slack Motors
Address: 1635 N. E. Sandy Blvd.
City: Portland 12
State: OR
Zip: Information I have predates use of zip codes (12)
Year: 1967
This information is provided from my tank sticker and Warranty booklet. Photos of both of these documents were emailed to Al Grenning in May 2002. I sure would like to talk to somebody who might know someone who worked there, knows who took over the dealership, or knows where some of their records might be. My business phone number is 412-921-8544 (voicemail). Thanks...."