As Stage2 Iron said already your transmission is a '73 model. More specifically it is a 1973 with a code of "OD" which is a 1973 Oldsmobile Cutlass, 455. A Buick would have a transmission with a two letter code that starts with a B. Here is an Olds site the confirms it as well: https://www.tpocr.com/oldstc.html
Block Stamp looks pretty legit to me. Only GM's "quality is job none" employees could make the stamping look that bad unless someone truly tried to replicate the whole scene by having a few drinks beforehand & having a cig hangin' out of their mouth w/the smoke goin' in their eyes while re-stamping it. Post pics of all the stampings on the deck (driver's side between the plugs).
What's the stamping look like of the engine code near the two rear spark plugs on the driver side look like ?
That last picture above, looks to be on the head , never seen numbers on the head before, do I need glasses?
Is there a 71 on the number one exhaust port above the exhaust manifold next to the power steering pump ?
That’s irrefutable evidence of foolery wouldn’t you think? Heads were never stamped with any numbers on any GS
Those stamps look nothing like the pic OP posted of the block stamp. Certianly someone added them to the heads but doesn't necessarily mean anything fraudulent. Could've been as simple as wanting to identify them when the engine was apart as being the heads that went with that block.
With that engine stamp and the heads on a 1971 no documentation, wrong Olds Tranny............grandpa always said “smells like a duck, looks like a duck...must be a duck”..... just sayin.......the author asked for opinions and if I was looking at it to purchase I would be very skeptical if I was wanting # ‘s matching.
Can't disagree there - I'd like to see the stamps on the deck would really need to look more closely at the block stamping. Idk how much value the #'s matching trans adds/subtracts &/or if was sold that way.