Vin, Body Tag, and Engine Code Information
Short answer: The number on the body tag and the VIN won’t match — that’s normal. The VIN is the sequential production number; the body-tag number is the Unit (consecutive build) number. They’re separate systems.
Engine stampings in this example:
- 508743 = Motor (engine) Unit Number
- YJ = 8-cylinder, 326 cid, 250 hp, 9.2:1 compression, 2-barrel carb, automatic transmission
- The “GM4” block casting marking’s meaning isn’t known.
Sources: Firebird Red Book; Catalog of Firebird ID Numbers 1967–93; Pontiac Historic Services; Year One catalog.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: June 13, 2026 at 10:06 am
← Frequently Asked Questions
