How to I.D. super stock springs

We are starting on our 71 RR.
Original Cal. car a N.Y guy started to redo until he found the Dart of his dreams.

All the suspension parts were either replaced or reconditioned.
Pulled the 8-3/4 to get ready for the Dana and wondered what we had for leafs.

Rear springs look new with the extra half-leafs ala HD suspension.

How can I differentiate between HD and SS? Arc, spring thickness or another ID?

Thanks, Joe

part number on bottom leaf?

I'll look....thanks


P4452983 on driver's side, didn't see a # on pass. side.

What do we have??

Thanks, Joe

Looked it up, std. HD springs,
thanks 6bblgt....Joe