Try looking in more local stuff, unless you live in the rust belt. The deal will not be in a national publication or site with a tight focus.
Of course, you can check out Hemmings, Ebay, sites for the car you are looking for and even racing junk. Cast as wide a net as possible, if only to gauge a good deal when you do see one.
I was looking for a 46-48 Plymouth 2 door sedan for months. Every one seemed to be a bit out of reach or a mess. I ended up with my 47 Chrysler, and while it's not the exact car I wanted, it's been a neat car.