Fellas -
I'm doing a leaf springs gig on my Ramcharger and it'll also be 6BT-powered. In my research I've discovered that most aftermarket spring mfg's don't carry the big heavy duty springs for the Dodges. But, there are a couple that I found that'll work.
What I'm doing is using a Pro Comp '85 K20 Suburban front 3/4-ton leaf and having a custom top leaf made locally with the Dodge eyes. Also, I'm having the spring made to accomodate a 1-1/2" bushings front and rear. The Pro Comp spring is very beefy - has a military 'wrap' second leaf, best I have come across, and should handle the Cummins weight quite well. The problem is the Chevy spring is about 2" shorter than the Dodge, but if you're looking for a good spring I think the Pro Comp is a good way to go if you can get a Dodge top leaf made for it.
If not, Superlift makes a pretty beefy Dodge front spring and has the stock Dodge small bushings. Not necessarily a drawback, but it'll bolt right up.
- M2