This was held at Westworld this year. My wife and I went for the first time, after hearing about it for years. We went on "Family Value Day", expecting the masses, and there were plenty of people, but the organizers have it all down, as to parking, shuttles, lines, etc. So you don't really wind up waiting too long and the atmosphere is fun. We spent a little too much time (yet loved it) looking at the newer sports and racing cars nearer the entry area, and spent a lot of time in one tent looking at and photographing a lot of the vintage and antique (like a Model T!) but lovingly restored cars and trucks. So we never did get to see a good chunk of everything else.....but that means we'll have to come back next year and plan better!
Tip: It's a photographer's paradise, because there are so many unique vehicles and the lighting, color, and curves are all fascinating. So bring some camera (with a flash, as a lot is just under tents) and have a wide-angle lens to capture the curves and most of the car.