External tranny weight?

Evening folks,
I picked up an '88 Grand Fury for parts the other day and it makes a whole lotta noise from somewhere in the drivetrain. I pulled the driveshaft tonight and replaced the rear u-joint, but I'm not sure the old one was bad.
Anyhow, I noticed what appears to be a large weight on the tail shaft behind the transmission mount. None of my reference material show or list this part, but it is loose. It is held on by two bolts, and it is loose enough to rattle. I'm hoping that this is most of the noise issue. Two questions,
#1, what exactly is this part and how tight should those bolts be?
#2, I also noted that the tranny mount sure doesn't look too good. I've not seen one (of the round bolt through designs). I will look at a new one at the auto supply as this might also be contributing to the noise.
Ok, so it's three questions,
Thanks in advance,
C