So perhaps this is pretty obvious, but took me a while to figure out.
I recently de-goated my 91. while taking off the heat shields, I ran into a tremendous amount of rust on the screws, nuts and back side of shields. All of the 5 screws wound up getting stripped despite my best efforts at using combination of PB penetrating spray and impact driver over a 24 hour period.
So I simply pried the other side of the bracket over the little lip holding them together and took off the heat shields and figured I would tackle the re-installation later. Had to end up using two sets of vise grips to get all the old screws out, and bought replacements from Home Depot that had hex heads instead of philips.
Needless to say, those failed miserably upon assembly, because the threads of the nuts that are welded to the straps were rusted too badly and too damaged to be re-used.
After some thought I decided to buy some hose clamps and JB weld. Figured I would "weld" the hose clamps to the inside of the heat shield right next to the existing brackets and then strap them around the exhaust. After getting two of them attached and using an entire package of epoxy, I realized the original welded attachment brackets are not flush with the inside of the heat shield, and that in fact there is a channel behind each one that is the perfect size to slide a hose clamp through.
So, moral of the story, look carefully at what you are trying to fix and don't over-think it.
Also if your heat shields' brackets are in bad shape, just buy a few hose clamps and slide them in, they work better than the original setup and are far easier to remove/install.
Thanks for listening