I took my leaf springs to local 'old school' spring shop, first thing per the expert was to make a new main leaf, which helped a lot. I'd also consider a pair of air schocks in the rear, that way you can add or subtract the air charge as you need.
Good luck

It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed