[GMH454]

Welcome. You have a real niche item, the guys here are pro Camaro / Drag, not Vette / Enduros. Greenwood had a special relationship with GM. For ppl like Penske, Mclaren Greenwood the engines they got received different stampings on the engine pad that are totally unique. As these blocks turn up so infrequently this fact is pretty well unknown.
If you can find any trace of a stamping on the pad please PM me. Don't look for a VIN style stamping the codes are totally different to what was put in cars.