We have been through this before haven't we? Didn't we find the parts are the same numbers or fit the same vans, all have the same ratios, same brakes, etc. If anyone feels better believing they are beefier on the 3500 fine, you show us please, I'm not going through this again. Yes early on FCA did say the ratios were different but that proved to be erroneous IIRC. There were several spring part numbers but they pointed back to all three levels of van. If you need the extended you bought a 3500, good for you. If you bought a 136 you got a choice and both are the same so save the $1000 by purchasing a 1500. If you got the 159 you get to choose a 2500 or 3500, buy a 2500 and save the difference in cost. Perhaps uncubed's idea is a good one to show those springs are different. KOV and I have compared my 136 1500 and his 2500 159 and we both felt mine seems softer riding but....... it's a year newer and its shorter so the comparison is difficult?