I have been working with the search results for the past 1.5 hours without finding the info I need. I have found a lot of really good info along with all the notes I've taken on this subject but still no joy.........

Today I was given a full set of springs and Rancho shocks from a 2003 F-250 4x4 FX4 (I forgot to ask what motor and cab/bed config) with approx 25k miles on them. The truck was sold off two years ago so I can't check the door jamb sticker for the codes. I have searched here and several other placed on the interweb and have yet to find anything that matches what I have found on the springs. Hopefully someone here can help make some sense out of this for me.
The numbers stamped into the springs are as follows,
Fronts 2C34AFA RPN2742
Rears 2C34CB RPN2552 (on one) RPN2692 (on the other)
These don't match up with anything I've seen in the dozens if not hundreds of threads on the subject that I've read here.
I did find one list that shows an "X" code with a number of 2C34-5310-AFA, close but not a match and a "B" code as 1C34-5560-CB (or) 3C3Z-5560-CB again close but not a good match. As you can see my first number/letter group is a match on the front and close on the rears and both of my last letter sets are matches. But I'm lost on the middle number sets, I'm nowhere even close to a match, or am I way off base and the Part #'s and the spring stampings are not suposed to be a match totally? I don't know what the "RPN" signifies, and why are my rears different?
The price was right (FREE!) and I am hopeful that these are winners, we tow a 10K ToyHauler and a spring upgrade should help to make the Ex a little more comfortable. It gets kind of exciting sometimes now, the rear Hellwig sway bar helped some but it still needs some help.
Any and all help gladly accepted folks!
Thanks!

 

Below are some spring codes that I was using when I looked for mine. You have the X code for the front but I do not see a match in my list for the rear. If I stumble across anything else I will let you know. Maybe pictures of the rear springs would help for someone that has seen a lot of them or at least it may help rule out what they are not. I did the V and modified B spring swap and am very happy. The codes on mine were V code (2C34 ADB) and B code (3C34 LC). Both of these were verified with the original trucks door stickers. I went with Bilstien's valved by Caryt. Ride is great and handles our 9000lb trailer well even with 35" tires. Yes - your price was right. I found the fronts from a guy at work that did a front level kit that replaced the springs - gave him $75 and found the rears at a junk yard for $125. Both from low mileage trucks.

2003 manual
Front Springs — F-Series
B — F81A-5310-EA
C — F81A-5310-EA
D — F81A-5310-EA
E — F81A-5310-EA
F — F81A-5310-FA
G — F81A-5310-GA
H — F81A-5310-HA
I — F81A-5310-RA
J — F81A-5310-JA
K — F81A-5310-KA
R — 2C34-5310-AAB, 3,600 lb.
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.
Y — 2C34-5310-VA
Z — 2C34-5310-WA

a 2004 F SuperDuty:

Rear Springs — F-Series
B — 3C34-5560-L
C — 3C34-5A975-D
D — 3C34-5A975-G
E — 3C34-5A975-K
J — 3C34-5A975-J
M — 3C34-5A975-E
N — 3C34-5A975-F
P — 3C34-5A975-C
S — 3C34-5A975-C

 

Thanks for the reply, I thought the fronts might be the "X" codes from the number. But whats up with the 4 digit number in the middle? Thats where I'm lost, is IT not on the spring? When I looked at the springs I assumed that the RPN# was that middle group and thats what got me stumped.
Thanks again for the help. I think I saw your list during my searching but it was a little longer and had a second set of numbers for F-Series rears that included the 1C34-5560-CB which is pretty close to my number. And the "B"codes are the only springs I've seen listed anywhere that have the "CB" suffix.
Thanks again, reps given to you Red!

 

I looked around a little more and found where someone else also thought they had a B code 2C34CB and asked for help. I did not see a response. I think the 1C34CB and 2C34CB are older model year B codes and then the number changed in 04 to 3C34L. Not sure why Ford changed these numbers so often. I was told not to worry about the middle numbers or the RPN numbers as they seem to be all over the place. I think I would concentrate on verifying just the stamped number 2C34CB. Someone else must have seen this number and been able to verify it with a door code. Maybe you could post the question in a general forum for the pickups instead of the Ex forum and ask for some guys with 03's to check the door sticker for B code and then the spring stamp. My B codes have 4 leafs and then the bigger bottom overload. Some B codes also had the top overload.
Are you going to do modify the B spring by using your spacers and bottom two Ex leafs? I put a picture of the mod in my album. I would recommend the mod. I love how the rear of the truck rides with this configuration - very smooth yet handles a load. I have not yet been to a scale but estimate my tongue weight around 900-1000lbs. With the WD hitch I can level the Ex and it rides the same with the trailer as without.