Sweet. SPID is "special production ID" and the label inside the glovebox door has all the option codes for your truck's original equipment. It's how you know what was on the truck when it left the factory. The RPO (regular production option) code for the Sport package is BYP.
You've got a pretty cool truck on your hands. Here's a thread dedicated to them:
Chevy Sport Truck questions
Got any interior pics?