I have an older Retrosound Zuma in my '75 Targa. I used the Becker-style knobs and went through a couple of baseplate iterations. Here's the latest (and there are more examples in the rest of the thread):
https://forums.pelicanparts.com/porsche-911-technical-forum/700719-anybody-have-retrosound-head-unit-their-911-a-2.html#post11006187
I have some Boston Acoustics speakers in the doors and in the rear seat delete that I made. I'm not running an amp. That head unit looks good but it doesn't sound great (maybe it does need an amp). I have often thought that if I had to do it over, I think I would chase one of those Continental units - but it might not look right either.
I'm willing to share my baseplate design if you elect to use one of the Retrosound Motor 4HD build-a-DIN unit...