Re-arching Leaf Spring question

Car is a 67 Dart Convertible - 273/904/7.25. Leaf springs sag, passenger worse than driver. We have a local shop here known for their work, and I am pulling them tonight to have them re-arched.

My question is this - are the springs the same for either side from the factory, or are they different? I know the high performance cars were different for launch torque, but what about the standard models?

I want the car to sit level (left to right), and ever so slightly raked (back to front), so my plan is to tell them to put an equal arch in both springs (assuming the springs are the same). if someone knows something different about getting her to sit level, please help.

Side note, I will be putting in an 8.75 next year - do my leaf springs care what axle and rear end are in the car (i.e. will that change the stance at all)?

Thanks FABO