1968 Barracuda Dash Speaker Access, Size & Replacement

I made my own speaker bracket by tracking the original speaker. I think I was able to mount two 4" round speaerkers, but they may have been 3.5". I think they were Infinitys. For a head unit, I used a round marine guage pod radio in a homemade console. Radio is about the same size as my tach that still isn't connected.