1968 Leaf spring code 132

I have the rear suspension apart on my 1968 Barracuda Fastback. I noticed that it has 6 leafs on both side and a 5/8" front mounting bolt. So doing measurements, the front eye to the perch pin is 20" and the leafs are 2 1/2" wide.
Checking the broadcast sheet, I see that it was marked Rear leafs right and Left side as code 132. Is this what they called the HD Suspension that went in 340 cars or did someone add different springs during its life?
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