Help with leaf springs

I want to change leaf springs and some guys say dont use SS springs. I have a friend who has P3412002 from Mopar Performance and p3412003 Summit show them as a competition spring will both sides be the same height? This is what im trying to stay away from, One side being higher than the other, can someone educate me. this is a street car not a drag strip car. Car is a 67 barracuda, 8 3/4 360 engine auto.