I used google image search and it appears that this comes from a Japanese book that is a "world police catalog" with the year stated on it being 1978. It also contains pictures of more vehicle, though they aren't from LA, beside a picture of a LASD van. But I did find another website that had an extra page to preview and it contains a few CHP vehicles. https://history.aucfan.com/yahoo/h1026174156/ask/ and https://page.auctions.yahoo.co.jp/jp/auction/o440507340 are where these pictures can be found. It seems to be a e-bay type website so you might even be able to buy it, it seems. Honestly I think it might be a good idea to start using google images more often, I didn't realize till now that this tool is really useful, you can use it to find the original source which can lead to even more finds and if you find nothing from the original source, you can always copy an image of those old cars and paste it into google image search and it gives to similar pictures. Edit: I have continued to search and I noticed that i'm seeing a lot about this Wild Mook thing, looked it up and it's published by a guy named Haruo Mizuno , he loved American cops and managed to get ride alongs with NYPD and the LAPD and has apparently published "about a dozen books on this topic", so that might be something to follow.