As the owner of a pretty original sublime 1970 340 4-speed swinger two owner car I have always been conscientious about keeping it as original as I can within reason. My advice is don't make any changes that are hard to change back. For example lots of people minitub and move there leaf springs in only to pull it all out a few years later to go back original . Dusters and demons will accommodate large drag radials that fit under stock suspension ish cars with a little bit of work and are capable of holding a lot of horsepower and pushing a car into the low 10s. And faster.