So I cheated like hell and bought a used good tranny from a local Mazda shop. $450 OTD -- my third gear was going out anyways (203k on it).

Was careful in aligning in and homegirl just slid right in. Great success!

DUMB QUESTION: it looks like this thing was filled with some amount of motor oil before storage, so I'm wondering, I should give this thing a good flush, right? My plan was to run cheap 75W through it until the oil came out clean starting with letting it drip through the driveshaft input then moving to the actual drain bolt. Need to do any more than that?

 

After your planned fill and dump, put the trans in the car. Fill with the same oil again. Run for 20 or 30 miles gently, then drain again and fill with good oil.

Oil is sticky and will stay on all the gears in a simple rinse. Running it heats it up enough to exchange what sits on and between the gears and in bearings