When I shipped my tranny I got a good pallet, preferably one made of hard wood, sat the tranny on it, blocked the sides and built a plywood box around it. I had the box screwed down to the pallet and the front flush with the front of the tranny and bolted through the plywood into the housing. You could put acouple of straps over the tranny first if you want before you build the box. You could have dropped that sucker out of a plane and not hurt it.
When it got to ATS there was some serious grousing about getting it unpacked, but what the hell it got there in one piece. I shipped with a trucking company called Oak Harbor freight, very reasonable in shipping price. I'm sure they have them in Spokane.