Whatever the auto parts says will fit, thats what will fit?
Sorry for the smart azz answer but i can think of only one solution if you require additional power, on our work trucks (a pickup truck Ford with trition V10 i forget the model number). we have a seperate battery wired in to provide more juice for jump starting. So maybe you can add a seperate battery in the trunk. And run your gigantic stereo system off that. I didnt do the wiring so i cant tell you how to do it but im sure someone here could.
All i know is you'd want to be darn careful if you tried hooking them in series or something so you dont fry your wires. Anyway thats my two cents, i found a posts from another forum someplace that may give you some ideas.
http://www.mustangforums.com/archive...-673087-1.html
http://forum.ecoustics.com/bbs/messages/4/129289.html