To do before car goes up for tranny pulling

Barbee6043 mentioned draining the transmission fluid. I would definitely do that.

Other than that I can't think of anything you missed.

I never put mine that high...too scary for me!! I get the car up high enough to get under it, pull the transmission with a floor jack with a 1 x 4 on it. Then I slide the transmission off the floor jack onto a piece of cardboard and slide it out under the front of the car. Bam!

Good luck. My list includes rebuilding my 904 at some point. Just gather all the resources, books and videos and review them over and over before starting. Sounds like fun!!!