I literally had a post scheduled to post this morning on GBN related to this, maybe it will help some, but 69hurstolds pretty much laid it all out.
What Info Can I Get From My G-Body VIN? - GBodyNation.com
What Info Can I Get From My G-Body VIN? Decoding G-Body VINs and Trim Tags.gbodynation.com
The Engine code is often the only way to tell if a car is, like in the above example a real H/O, or like the Monte Carlo SS, would have a 7 or G (depending on year) for the “High Output” version of the 305. The R code also signified the “high output” 307 for the later Olds 442 cars.
GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.