TSB
Darren,
I did this TSB to my 2500 and am sorry I didn't do it sooner. It made a very noticeable improvement in braking. The replacement hose was $26 at the dealer. The TSB does not address the 3500 but cannot understand why.
You could do like another gentleman suggested; Disconnect the proportioning valve linkeage and wire tie ithe valve to the full open position and try it out. I think you will be pleased with the results. If for some reason, you don't want to do this; Simply reconnect the linkage.
Good Luck,
Frank