? on 7 1/4 to 8 3/4 rear end

I have a 66 dart that I am putting a 360 in it. I am also going to swap out the 7 1/4 for an 8 3/4 rear end. Will my existing driveshaft fit?? if not, does anyone know how much it will have to be cut?? Or does anyone have one that will bolt in??? Thanking you in advance, John