There are 5 unopened packs of Monster Truck trading cards plus 3 cards from a pack that I just opened.  They are dated 1989 Leesley Trading Cards.  There are 5 per package.  That would be 28 cards total.  I found these today with some pit passes.  Also 1 TNT bumper sticker, 1 Red Man pit pass holder, and 6 pit passes. 1 pit pass from the Monster Truck Challenge in Nashville, TN in 1988.  2 pit passes from the TNT pull in Stafford Springs, CT in 1988.   3 pit passes for the TNT pull in Delmar, DE in 1988.

I think that the trading cards were either given to kids at the ticket gate or sold in the souviner stands.