Keep your Caterpillar 3300 Series engines up and running with parts from Spares Trading & Agencies Co. When the 3304 and 3306 Caterpillar need service, you can rely on us to supply the highest-quality new and engine parts. All of our engine parts are rigorously tested and adhere to manufacturer’s specifications. So whether you need new Cat 3304 diesel engine parts or a alternative, you’ll get years of reliable operation.