Rear width/mini tub?

I drug the 67 post valiant in today and am having many thoughts on which way to go so here comes the questions. I would like to have rear meats of at least 10-12" wide. Do i need a narrowed rear to put on these wider tires? I plan on doing a mini tube if i need to. I guess i'll have to do a spring relocate to make enough room? If so some pics of a finished job would be helpful. The original color of the valiant is BB1 black but i think i'll play a little and do some green and silver. Your thoughts please.