If you're running headers, wrap them. An air intake in or under the air dam ducted to the engine compartment will help. If your inner fenders had a couple vent holes that would help, too. Or, a NACA duct on the rear of each fender ducted to the underhood compartment will exhaust some of the heat.... Unless it's right on the ground, can't really see where there wouldn't be enough air flow under a pickup.... Might want to get an insulation panel for the starter to protect it from the exhaust heat if the exhaust is close to the starter.