So....having one of numerous machinists I know around town build a spacer, free of charge. How cool is that? At some point after I've worked all the bugs out I'll make a comprehensive list of issues and the fixes, part numbers I used etc. One of the mods can add it to the appropriate spot.
In case you were wondering what the valve body/TCM assembly looks like here it is. The filter is made into the pan, I plan on installing a deep aluminum pan with a replaceable filter and a provision for a temp sensor.
I finally got around to pulling the pan off this boneyard trans a few days ago, figured I had better take a look before going any further. Has a factory reman tag on the case from 2019 and is really clean inside. Nothing stuck to the magnets in the pan, doesn't stink like burnt fluid or any of that. Only paid $550 plus freight for it, hopefully it works as it should.