When you take the driveline out to fix those ujoints grab the back of the trans and give it a good yank up and down and sideways and you'll see it.
It bolts to the crossmember and the trans both.
4 long bolts with nuts hold the crossmember to the car body and two bolts go up through the mount flanges into the trans case.
You might even consider replacing the cork gasket under that little plate with the big phillips screws in it while your in there anyway.
A lot of people don't know it's there since it's kind of hidden under the mount.