New to A bodies, not to Mopar

Dartnut said

Welcome to FABO, good looking project you have there.
As far as lifting the rear end up, I would go with 002/003 Super Stock springs.
I did it to my Dart Sport, and love them.
Your car has a '70 to '72 Duster/Valiant front clip on it, if you didn't know.

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Thank you, yes I was aware of the front clip, but wasn't sure of the model year. I'm actually pretty happy with that, too, because I favor it over the "pointy" design of the later models.
Is there anything I need in regards to spring installation or are they a simple remove and replace? Shall I just modify the shackle kit on this for the rear mount, to around the correct length; and if so, what is that length? I'm not new to replacing any part on a vehicle - I've been a tech for a long time. I haven't built a car in decades, and since I didn't take this one apart and it came in pieces, it's messing with my mind a bit.