I am of the "stock sucks" crowd most of the time. But that is too nice to cut up I think. Like was said in another post, maybe wheels and a drop. Nothing that can't be undone easy. Some cars just shouldn't be changed, but I wouldn't ever own one of them.
I think that interior looks great. I wouldn't do anything that could not be 'unbolted'. I agree with the comment about a possible wheel/tire change. I would consider a bolt-on front disc setup if I was going to drive it much. Cool car.
Leave it alone, don't mess up a good thing. That is not a barn find ready to be done up, it is perfect the way it is. If anything put wheels on it and leave the rest alone.