351C where to start?

There's not a whole lot to decode on that vin. Its only a partial. I think you already got the year-1973 and the plant was Atlanta. The rest is the sequential car number it came from. There were a handful of cars that came with a 351C, made in Atlanta in 1973. That could possibly be a ranchero or maybe a gran torino?

Nothing about that suggests that the block is not worth the effort. You may be dealing with a rebuild motor, or somebody could have pulled a complete motor out of a different car to plop in.

I'm not sure about the engine block casting letter "A".
If that motor is otherwise good, it probably should be a 4 bolt main, not that the extra bolts actually do much, so could well be worth rebuilding to whatever spec you want, keep it stockish or stroke it.
I'm definitely not the engine guy around here, so I'm sure others will chime in to help out.
One thing is for sure, you don't have the original motor in there.

Block Casting is D2AE-CA
Production Date: 2k26 (26 September 1972?)

According to Enginelabs.com: D2AE-CA – 1972-1974, 1971-1974, 351 Cleveland small-block, 4-bolt mains, High Output, Cobra Jet, Boss

I know I need to look in the pan to verify 4 bolt main but that's cool. So how do I figure out if I'm working with a high compression 72 HO or a detuned 73 CJ? I'm really kicking myself for not getting head casting numbers. I guess I can use borescope to peak in the oil drain to verify 4 bolt, peak in the spark plug hole to see flat or dished pistons, maybe be able to tell if open or closed chamber heads (but guessing from production date probably open chamber)?

I know this could all be a moot point if the engine was rebuilt before and the only absolute way to tell is to tear the engine apart; just trying to get as much info as possible to figure out where to steer this ship. Next up is to order the timing set and try to get it running correctly. Any thing else I should order or be on the lookout for while I'm in there?

Edit: I am kinda getting hung up on whether this is the higher compression engine or the low output 73. How big of a difference is it really? I am not ready to do a full engine overhaul so just hoping im starting with a better foundation.

351mach1,
The 1972 HO engine (as delivered) should be a solid lifter engine and therefore (should ) have screw in rocker studs and adjustable rocker gear with open chamber heads.
The CJ (should) have hydraulic camshaft, pedestal rocker arms and open chamber heads.
Boilermaster

I have a theory as to why nearly all 72-73 351C motors had 4 bolt mains;
As ALL the blocks cast could be drilled and tapped for the extra bolts, Ford produced way too many 4 bolt caps. Only certain 70-71 351C blocks got the 4 bolt option. The M code was only 2 bolt for example.
SO, as they had all these extra caps on hand and as the production line was already set up to add the extra 5/16-18 tapped holes, why not use them up.
From what I understand, the smaller bolts are there only to stop or reduce fretting, sideways movement, so do little or nothing to add strength. The main bolts hold it all together.
As for your motor, for now, get it running and worry about what's in it later. An option might be to pick up a 351C block and build your own motor later.

While waiting for the timing set to arrive, I wanted to keep making progress: I stuck a bore scope down in a spark plug hole and I am about 95% certain this engine is a 74 CJ. The picture wasn't the easiest to decipher but there appeared to be dished pistons and open chamber heads. No surprise there really. I am kinda bummed that I didn't know what I was buying but it's all part of the game I guess!

The Chinese garbage sourced from the local auto part stores is really disappointing. Wasted 2 nights of my life on trash "refurbished" starters. Is there anywhere to source quality OEM starter, alternator, distributors? I guess I can take solace in the fact that I can replace these parts as much as I want with their "lifetime warranty"

I wanted to eliminate as many potential problems as possible to ensure everything is working correctly. The Duraspark currently installed was a total mess so I bought a new duraspark wiring harness, box, and ignition coil. I am struggling to find the correct distributor that fits under the Ram Air. I will be making separate posts pertaining to the duraspark conversion and hacked wiring harness. I will return the Pertronix system I bought and stick with the duraspark.

With the fresh ignition system, I got the ol gal to fire up! She was kicking back a little bit at first (probably didnt help that it was 35 degrees out) but once she warmed up, she idled and revved quite nice!! I even took her for a victory lap around the block. Pretty excited about that!!

So far I replaced the intake manifold, carburetor, and ignition system. The original complaint of backfiring and hesitation while driving is gone. The car isn't nearly as peppy as I would have expected and I am wondering if that is still a symptom of the timing chain or more so engine and transmission combo. Since it currently runs, drives, and stops, I think I am going to shift focus to getting it legally inspected and registered before diving into the timing chain. I will follow up with this thread when I do the timing but for now I think its time to start a build thread and ask a few other questions that are probably best saved for their own threads.

I really appreciate all of your responses. Keep em coming and I'll keep posting!