When I replaced my cat converter mount I found that the bolts that hold it to the chassis also holds the tranny.
I used a about a 2 x 2 foot piece of plywood and a floor jack on the tranny pan. I just went real slow after I clean the mounts and had a good light to see what I was doing.
It will take longer to jack the car up and get it on a ramp or stands and get the jack under the tranny than it will to change the mount. The space is a little tight under there.