When you added the helper leaf, did you check for cracks in the main leafs? My 1980 main leafs cracked front to back from the center hole about 4" and I had to replace them - the other leafs were fine.
The best Dodge that Dodge never made
Living the D-50 lifestyle since 1980
The wrench who installed them for me had them out on the bench and didn't mention anything about cracking. (Decided to have his shop do it for $80 instead of spending a day in the driveway trying to get it right These are an aftermarket set of Rancho "reversed" springs I think ... The guy who built up the truck did them for over-axle.
I remember some paperwork about reversing them. Hopefully they are stronger than stock. If not, there is always Bentz Spring here in Portland; they make the best.