Thanks for everyone's comments. Speaking from an unfortunate experience, what I can say is don't let the tow truck driver just hook up to the left or the right tow hook!
Here's what BMW NA had to say (couldn't find any official Certified Classic Centers in California - just links to regional dealerships):
Dear Mr. Myers:
Thank you for writing to BMW of North America, LLC regarding how to properly tow your 1974 BMW 3.0CS. We appreciate your inquiry.
For newer BMW's, we suggest using both tow hooks in the front bumper to properly tow a BMW on a flatbed. Additional information should be available in the Owner's Manual.
For specific tow instructions for your vehicle, we suggest reaching out to a BMW Certified Classic Center for additional information. Unfortunately, I am unable to locate an owner's manual for your model to provide you with the proper instructions.
To locate a BMW Certified Classic Center, please visit
http://www.bmwusa.com/Standard/Content/Owner/classiccars.aspx.
For your convenience, the BMW Customer Relations and Services Department is available Monday through Thursday from 9:00 a.m. to 9:00 p.m. ET and Friday from 9:00 a.m. to 6:00 p.m. ET. You can reach us at 1-800-831-1117.
Thank you again for taking the time to write to us.