Thanks again John.
I managed to save myself a bit of money, and a lot of work.

I found a used, but rebuilt with stronger internals, trans that'll bolt right in. Got it for a fair price.
I do have the FSM, but it turns out swapping in stronger gears is not as cut-and-dry in my model-year as it is in the newer WRX/STi models. Thanks Subaru for changing things up just enough to make it hard!!
Now at least, heaven forbid I bust something in this newer trans, all the strange "conversion" head aches is done. It'd be an easy pull/press to fix it.