FINALLY!! Found it!
Thanks for your help Buddy, it was stamped right on the edge of the casing on the drivers side behind the linkage and buried under 1/4" of crud. The partial VIN matches the car's VIN, and does not have the 6/9 issue like the engine stamp. Maybe the worker saw the mistake in the engine stamp and corrected it for the trans? Here are pics below of the trans stamp, and another good shot of the engine stamp.
So, what I have is an engine code (V022IMS) that matches the protect-o-plate, and the VIN is one number off (189552 vs. 186552). Maybe I asked this before, but if the engine code matches the protect-o-plate does that mean this is 100% the correct engine, or could the engine from car# 189552 had the same engine code and somehow a previous owner found this block? This would mean the 189552 car would have happened to have an L48 engine built on the same day at the same plant, and had a Muncie 4speed. I guess it's possible with the volumes that were coming out of these factories, but unlikely considering all the coincidences that would have had to take place.
Thanks again all, I love the car, and having a blast enjoing it the way it is until I figure out how far to take the restoration. I find all of this decoding fascinating, it is so awesome to have a community of people who are this interested in the details of these cars and keeing them original!