A couple of years back I rode bikes over with a few friends. I think they said they had around 400 cars for the cruise.
October 19, 2007,
21st Annual Robbers Cave Fall Foliage Cruise, Robbers
Robbers Cave State Park, Wilburton, OK. Free registration limited to pre 1979 vehicles. Early registration and Gearhead Gathering Friday, October 18th, 3pm - 9pm. The event is held at Robbers Cave State Park, North of Wilburton on Hwy 2. Free registration is limited to pre 1978 vehicles. Over 50 awards, dash plaques, event shirts, arts and crafts, food booths, amusements and entertainment. The Fall Foliage Cruise is held in conjunction with the Robbers Cave Fall Festival. Early registration and House of Packard Gearhead Gathering on Friday, October 18, from 3pm till we turn out the lights.
http://www.robberscavefallfestival.com/cruise.html