HELP! - Stock Radio/Speaker Installation

[heavychevy]

I am trying to install the stock AM radio & speaker in my '71 Custom/10. The speaker fits in the bracket and has a removeable/adjustable bracket/brace/arm that attaches to the bolt extending from the back of the radio. Now, where this "arm" attaches to the bracket, there are 2 more holes about 2-1/2 or 3 inches apart that go somewhere. There are nut marks here on them, but after looking at the radio and under the dash, I cannot see where this end of the support bracket attaches. Am I missing parts? Does anyone have a picture they could send? This mounting bracket for the speaker, has 3 separate parts that bolt together to mount the speaker. If I use just this bracket, the ONLY thing holding the speaker in the dask would be the one support arm that attches to the stud on the back of the radio. What holds the speaker tight under the speaker grill, under the dash? Just this bracket? I might be able to accept that this bracket is the sole "holder of the speaker" if I could figure out where those 2 mounting holes bolt to, on the bracket, but I suspect I am missing atleast 1 bracket, of sorts..... If you are familiar with the stock installation of the radio/speaker, please help me out! Thanks in advance....Brian