Chevy Truck Engine Specifications, RPO Codes, Horsepower *RPO stands for Regular Production Option. That means an option available from GM when the truck was new. Almost everything has an RPO code. You can find a list of RPO's here. Complete Engines for Chevy 7/454 Engine for sale | eBay What You Need to Know About Chevy 454 Complete Engines. When you need to replace an engine in your Chevrolet, a complete engine assembly can be an option. This generally consists of the engine block, crankshaft, valve train, heads, and camshaft preassembled.