68 Plymouth Fury Wagon Rear Springs

I have been wanting to replace the rear springs in the wagon. They are completely flat with very little arch. The previous owner put air shocks on the car to compensate, I replaced the air lines a couple years ago because there was a small leak over time. Last year I had to air them up everytime I took car out as it would scape the new NOS rear bumper I put on 2 yrs ago.
I have contacted a couple local spring shops first one does not make new springs they buy the from some distributor out of...

68 Plymouth Fury Wagon Rear Springs