On the passengers side of the "small block Chevy" where the heads are offset a little is a code. It will have numbers and or letters. This code will not only tell you the year, but application as well (ie. HD Truck, Sedan, HP Corvette, Police Interceptor) Making sure that the engine is a HD application is as simple as removing the oil pan! The crankshaft journals should have 4 bolts in the main bearings. 2 at the crank bearing and 2 at the outer edge of the bearing retaining block! This is Chevy's "4-bolt main" you read about in all the magazines!