It also appears the rear shackle has took a hit to me..........take the shackle loose, make sure the springs align with the front shackle in correlation with the rear housing mount as well. A new set of bushings and plates should complete the job......and be sure to check out the front hangers as well.
Does the rear axle look original? Are both sides pushed out at the rear? If both are out, the axle mounting pads are to wide splaying the springs out at the rear. If it's only one side, then the locating pin on the leaf spring could be sheered off from some sort of damage, this will angle the spring out just as you have.
You should pull the axle loose from the spring to confirm no damage, then replace all the shackles and bushings. '37 spring bushings are made from a bronze alloy with a steel pin through them, you will need to keep them greased quite often. Also, don't over tighten the center shackle bolt either, just tight enough to not bend the plate is about right.
On a side note, when the springs are out, pull them apart and grind off any steps that may have been worn into them from use, and to help in the ride quality, add Poly-slide spring liner between each leaf.
