I had a set of 5,200# in my front end. I swapped them out for the 6000# springs, for the same reason- so I could plow. The only things that are added/changed to plow prep vehicles are heavier springs, and either the "extra heavy duty Altenator, or dual altenators. The axles and everything else is identicle. Easy swap. Order them from Tascaparts.com cost +10% $83.04 a piece. This TSB lists the spring codes and part numbers. If you order them from Tasca just don't enter your VIN on the order page, or they will assume you ordered the wrong part.
The ones you want are the set that end in ACC, those are the 6000# springs
PART NUMBER PART NAME
5C3Z-5310-CA Front Spring (ACC)
5C3Z-5310-DA Front Spring (ADC)
5C3Z-5310-EA Front Spring (AEC)
5C3Z-5310-FA Front Spring (AFC)
F-Super Duty Monobeam Coil Spring Rates (F250/350 4x4)
Front GAWR Rating Current Vehicle Spring Coil P/N 5C34-5310- Intall F250/F350 2-UP
4000 AHC AFC
4400 AGC AEC
4800 AFC ADC
5200 AEC ACC
5600 ADC ACC
6000 ACC No Replacement Part Available
11-4-19***4X4 ONLY - BANGING/CLUNKING NOISE WHEN DRIVING - CONTACT WITH JOUNCE BUMPER - COLD TEMPERATURES