Just picked up a 1968 Mustang Coupe and it has an aftermarket casette deck adn amp from the 80's it looks to be. What can i get the looks more period correct but has at least an AUX in? something like retrosound??

 

Retrosound and autosoundare the best original style stereos and I beleive they do haveaux in's...

Pretty much any of the original style radios will work fine.

Is the amp actually connected to anything?

I actually commited the tyranny of cutting the dash on my 65.As an audio enthusiast I cannot even use something like the autosound usa or retrosound unit.