If it's a JS23N1, it's without doubt a 383 R/T. That's about all you can glean from the VIN, along with the build plant. I'm guessing that you're saying no AC (there's no such thing as "AC delete"--it wasn't standard equipment) due to the firewall, which makes sense, but without a fender tag it's entirely possible it's not even a factory manual-transmission car, never mind a 4-speed. Cutting the floor and adding the tunnel extension isn't too difficult, and putting a 4-speed where a 3-speed once sat is an afternoon job. Of course, if there's a 4-speed in it stamped with a matching partial VIN, well, that's another matter entirely.
The world is kind of your oyster here. It's an R/T and it's set up for a manual transmission. Not having the data tag gives you the option of building it as you see fit, and nobody can tell you you're wrong... because they don't know what's right.
If information exists regarding which VIN was built with which equipment, either nobody's found, or dared wade into, that data yet. Apparently it did exist at one time, but what became of it nobody's quite certain.