I can't help with the Mechanix Illustrated plans, but I can suggest a couple of other possibilities. One is Taubman Plans Service, the operation of Mr. Abe Taubman, a remarkable character who sells plans for all sorts of vessels. I'm pretty sure his catalog includes a Cape-class patrol boat. I don't have his address at hand, but you can get it from the website of Ships in Scale magazine: <www.seaways.com>. Abe does have a website of his own, but be warned: nothing like his entire range of plans is listed on it. If interested, you should order his printed catalog.
My other suggestion is to go to the horse's mouth, the U.S. Coast Guard Historian's Office. The senior historian, Dr. Bob Browning, is a first-rate gent and knows how to get hold of the genuine official Coast Guard plans of every ship for which such plans exist. There's also a wealth of information on all sorts of CG history on his website. You can get there by going to the general-purpose Coast Guard site, <www.uscg.mil>, and following the links to "history."
Hope this helps.
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