The Pro Stock Semi OSTPA class in Ohio is a real crowd pleaser. While there isn’t many that compete with these big tractors, they always draw big crowds. The trucks themselves are beefed up Semi Trucks. The rules for these trucks is that they must be 20,000lbs or lighter with a 250 inch max wheelbase and under 102 inches wide. The drivers cannot move the engine more than 1 foot either way from the stock location and must have a complete firewall. Aside from that the engines, while they don’t have to be stock for the vehicle, cannot be complete custom units or use non oem heads.