Original Rear Leaf Spring Part #

I'm reaching here to see if I can get some help on my build. I'm working on a '63 Dodge 330 Sedan, Max Wedge build, which uses the A-body dimensions for the rear suspension. The original springs have a 20" front segment, with a 35" rear segment. I was wondering if anyone here has the original part# for the springs that came in the '68 Factory SS package ? I see Mopar Performance offers a spring set for this, P3412002 & P3412003. These match up, except the rear segment is 36" long. Any help, or info on this would really be appreciated, as I'm hung up on the rear axle install, until I get this sorted out. Any pics of originals would be great, front & rear mounts, Thanks...