Removing radio, replacing it with bluetooth receiver - how?

[MuffDaddy]

I've gone for this:


From here

https://celsusice.co.uk/celsus-universal-ip66-blue...

Although I don't have my car here at the moment. I'm looking to redesign and simplify the dash, I ony ever stream from my phone and I'm not that fussed about front/rear balance, once it is set on the amp it should be fine.