Ok, when I was swapping my battery out last week, I noticed that the hold-downs on both sides were gone (one missing, the other snapped off), so I ordered a new battery tray from Latemodel Restoration. After wrestling the two rusted bolts out of the fender skirt, the thing is still well held down by.... 'SOMETHING' .... All I can see is a rusty blob on the bottom left side (forward side) of the plastic tray, apparently tying the tray to the framerail. I presume it was either a bolt or a rivet. I cannot tell which. I am also not sure if it's safe to drill it out or what. There's a lot of stuff around there... brake lines, wires, etc.
I just pulled mine out of my 04 gt. mine did alright protecting the stuff from corrosion there was some on the lines and what not but nothing a little pb blaster didnt clean up. i snapped the battery tray off and sprayed some pb blaster on the screw and it came right out. you might find like my self there is some rust on the frame rail what im going to do is sand a bit and spray some primer just so it wont rust and wait till i get the motor one of these days to paiint the engine bay. but make sure that you rinse with water so that the pb blaster wont loosen any connections on brake lines etc.