rear disc and rear spring question
 

ok i am almost done with my rear end of the chevelle. i ran out of time today to finish off the other side of the axle but the one side i got done i am so happy with it! so today i was thinking about it. i want to finish the rear of the car. So i want to order some new springs and shocks for it. I was looking in the NPD and i found the springs but i see two types one is 49.95 and it says standard. and the other is 54.95 and it says HD (which i guess is heavy duty). which springs do i need then? i dont want to lower the car (yet) i just want it to be comfy. so would the standard springs work for me?

and for the rear disc i am really thinking about doing rear disc, but i was wondering since i have c-clip elims on my setup will disc brakes work with my setup?