Engine Identification Needed

Hi, I'm new to this forum and this is my first post. I have a question that I've had a tough time trying to get an answer to so I was hoping that someone here could give me a hand.

I've got a 1969 Buick Special Deluxe with a 350 2-bbl. in it. It's not original to the car, the VIN says that the car started it's life as an L-6.
In order to figure out where the engine actually came from I took the power steering pump off the front driver side of the engine in order to get at the engine serial number. It was really tough to read but I think I was able to get the numbers/letters right.
The only problem is after comparing them the Buick VIN breakdown they didn't make sense so I checked other GM VIN breakdowns and they still don't make sense.

Could someone help me? This is super frustrating so this would be very much appreciated.
This is the alpha-numeric engine serial number of the front driver side of the engine:
To be clear I'm not a 100% about the 2nd digit. I think it's a 3 but it could also be an 8 or a B.
Everything I've read and seen leads me to believe that the Engine Serial Number should only have one letter it (the second digit) but this is obviously not the case.

Thanks in advance,

Darcy

Darcy,

I would like to try to look into this further for you. In order to do so, I will need the VIN for the vehicle. Thank you in advance.

Tricia, GM Customer Service.

Hey Tricia,

That would awesome...thank you so much for looking into this for me.
The VIN is:

Darcy

I am going to do some research on this and see what I can come up with. I make no guarantees, but I should be able to let you know either way in the next couple of days. Thanks again.

Tricia, GM Customer Service.

I am stil trying to look into this for you, but I was wondering if there were any other numbers or letters stamped in the block. It is usually stamped in the block right under the head and can sometimes be found on the front or rear of the engine. You can also contact me by private message if you would like. Thank you in advance.

Tricia, GM Customer Service.

Hey Tricia,

Sorry for my late reply but for some reason I didn't get your last msg. until right now.
I'll take a look at it when I get up tomorrow morning. I'm actually in the process of replacing my harmonic balancer and when I was under the car this afternoon I noticed some numbers that I didn't realize were there until today. They were on the underside on the left side of the engine near the balancer.
The number I gave you previously was on the front of the block on the driver side right under the head, had to take the power steering pump off to get at it. The really weird thing about it was in order to actually see the numbers properly (aside from cleaning them and using a flashlight) I had read them from the driver side of the engine looking upside down. Not sure if this is normal.....doesn't seem normal to me.
The numbers for the engine code which are supposed to located between the first two spark plugs on the driver side (between the valve cover and the plugs) aren't there. In the diagram in my shop manual shows that there should be a small plate below and between the two plugs where the number should be stamped but there's nothing.
Thanks again for getting back to me and looking into this, I really appreciate it!

Darcy

Hey Tricia,

I was able to get under the car tonight and found the number I was talking about in my previous post. The number is located right above the harmonic balancer and after some searching I think this may actually be the timing chain cover part number however I could be wrong. Not sure if this helps or not:


Thanks again,

Darcy

Darcy,

Thank you again for the information. I will continue to do some research and I hope to get back to you no later than Tuesday. Thank you.

Tricia, GM Customer Service.

Darcy,

The only part of the cast number I could get to cross is the ARW and it crosses to a COLOMBIA EXPORT V8 366 engine 1966-1988. Not sure if this is correct, but let me know if it helps. Thank you.

Tricia, GM Customer Service.