Herb, here are the part numbers, approximate prices, and what the springs are rated for.
X Springs
(2) 2C3Z-5310-AF Springs @ $154.32 ea
(4) F81Z-5705-ZA U-Bolts @ $15.88 ea
(8) N805480-S426 Nut @ $1.86 ea
Ford makes several different front spring sets for PSD 4x4s. The computer at the "factory" selects the correct spring pack for your truck based on the weight of the truck and all the factory options. Generally, here are the different front springs available for the computer to select:
Code T: rated at 4,400 pounds @ground - common on regular-cab PSDs.
Code U (as in you): rated at 4,800 pounds @ground - common on SuperCab PSDs.
Code V (as in Violet): rated at 5,200 pounds @ground - common on CrewCab PSDs.
Code W: rated at 5,600 pounds @ground - usually available only on F-450/F-550
Code X: rated at 6,000 pounds @ground - available from the factory on pickups with the snowplow prep pkg, and on F-450/F-550.
Keith