A very big thanks!
Big Dave, thank you very much for posting all of this! I ended up placing the radio where it goes and everything became very apparent, minus the mushroom filler piece- was wondering what that was!
On a slightly different note, before my 64 radio I acquired a 63 as a gift. The 63 has a bracket that looks like it may have bolted to the ashtray housing. I went ahead and transferred the bracket, drilled a hole in the housing, and attached it. It may be "bad" in some people's eyes but it doesn't bother me, and now all 4 corners are supported.
Thanks again for the time and effort - I really mean it. I'm dealing with an issue on another vehicle, and have had ZERO replies to my questions.