No you spelled it right - Papadakis. It was on West 6th Street in San Pedro near downtown. I believe is was around in the early 70's and I believe it is still there. I have been there a few times in the 80's, good Greek food, and I believe the owners name was John. Anyway, if you want to live history and its still there give it a try.
Indeed, he drank at Musso's-after he got made. Always was high end and today a steak and martini will run you $70. If you come across references in his fiction to Hollywood greasy spoons I'd be interested. Thanks for the San Pedro reference.
Papdakis is a pain in the ass, and I can't imagine he went there more than once or twice. It doesn't strike me as his kind of place. It's formal, loud, communal and participatory. Not to mention ridiculously expensive for unexceptional Greek food. But if he liked it, he liked it. Seems uncharacteristic though.
Where they ate often - a couple times a week - was Senfuku, a very casual Japanese restaurant. We went there with Linda once and the employees treated her like family, so I assume she still drops in all the time.