if you have the donor vehicle it is on the sticker
This is what I have collected on Ford's front leaf spring codes:
S codes = 4000lbs capacity, 370 inch/lbs, 4.34" travel.
B codes = 4100lbs capacity, 330 inch/lbs, 5.02" travel.
C codes = 4300lbs capacity, 350 inch/lbs, 5.01" travel.
T codes = 4400lbs capacity, 390 inch/lbs, 4.63" travel.
D codes = 4700lbs capacity, 380 inch/lbs, 5.14" travel.
U codes = 4800lbs capacity, 410 inch/lbs, 4.89" travel.
V codes = 5200lbs capacity, 430 inch/lbs, 5.13" travel.
W codes = 5600lbs capacity, 450 inch/lbs, 5.34" travel.
X codes = 6000lbs capacity, 470 inch/lbs, 5.54" travel.
Capacity is per set.
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if ya have loose springs the part # is stamped on them
o R - F81A-5310-AAB, 3,600 lb.
o 7 - Six-speed manual, Dana ZF (M6HD-W),
o S - F81A-5310-AAB, 4,000 lb. F-Series (diesel)
o T - F81A-5310-ABB, 4,400 lb.
o U - F81A-5310-ACB, 4,800 lb.
o V - F81A-5310-ADB, 5,200 lb.
o W - F81A-5310-AEA, 5,600 lb.
o X - F81A-5310-AFA, 6,000 lb.
o Y - F81A-5310-VA
S = 2C34-5310-AAB, 4,000 lb.
T = 2C34-5310-ABB, 4,400 lb.
U = 2C34-5310-ACB, 4,800 lb.
V = 2C34-5310-ADB, 5,200 lb.
W = 2C34-5310-AEA, 5,600 lb.
X = 2C34-5310-AFA, 6,000 lb.
just some of the #s I found quickly