I've been trying to get spring numbers for months for my 98. 5 3500, 2wd. Ran into the same thing from the dealer, but they did tell me that springs fit from '97-'02. I had installed a NV5600 and it was over double the weight of the NV4500. Also had about 200K miles and the front end sat too low. After I found that the newer springs would fit, I knew where an '01 was that came equiped with the heavier trans. and it sat up very well in the front. I slid under the truck and removed the tag, ordered the new coils, and will install them this week. My original coils were #52039075. The better ones are #52113006AA and list for $106. 00 each. The best I could measure with a caliper, they were . 060 larger coils. The '01 truck sat over an inch higher than mine and had 215 tires where mine are 235's. This should do the job on the front, I'm waiting for some bushings and shocks so I can rebuild the front end. Was going to replace the ball joints but found the bushings bad so I will replace it all at one time. Don't have any info on the rears, mine has the helper springs and will tote a good load. If you know how or where to find the # on them, I will be glad to look for it. Good luck. Kenny N4YYX