I just got my brother into a 91 non-turbo and it has no stereo but he's got one to go in it. The factory mounting brackets are gone also. I've got some from an S4 and I wanted to know if those would work or a way to mount it without them sturdyly.

 

Well the previous owner of my car put the head unit in my car. They just used "L" brakets, and screwed them into the stock mounting holes, and into the head unit itself. It works really well it seems.