The 491295 is just the last 6 digits of the VIN number of the car it came in. The 4 is Buick Motor Division. On the 67 and up V8's, the second character is a number, the last digit of the year of production, BUT, you have an A there, so it must be an earlier engine. The H I believe is the Flint, MI plant.
Bob sorry can not do a picture of engine. The block casting number is 25505553, the number I got off of engine 4AH491295 on the block is located just above the oil filter housing. Number reads from top to bottom vertically. On left head where number one cylinder is there is a number 358 stamped into the head in front behind power steering bracket and a stamp that was put on using a punch that is TLW. Intake number is 25512236, It also has the letter T cast into it. On a spot on rear of engine where trans bolts up is a casting number that is 0120 and a casting clock which is at 12. Engine is painted a light blue. I think this engine is a 80-82 252 4.1 liter or maybe a 3.8 Don't know for sure. Those are all the numbers I could find. What does the 149 stamped in valve cover stand for? This is a V6 Buick in a 38 Willys Pickup. Thanks for your help Bob and Larry.
To add a bit more detail, the attached decoder card shows GM changed the VIN model year code to A in 1980 for some reason. It also shows the 4.1L was used only in Buicks that year. So the engine came from a 1980 Buick.
The Buick shop manual page attached shows the 4.1 L was supplied only in LeSabre and Electra models that year.
Have a 80 4.1 liter is there any difference in the harmonic balancer [lower] pully than on a 81-84? Whether it be a 4.1 or a 3.8. Fixing to buy March pullys and the 3.8 pullys they have listed only start at 81 3.8 and there is no return once I buy don't want to make a mistake and buy something that does not fit. Just want to make sure the bolt pattern is the same. Thanks