Nice looking rig.
I'm not a good source as I spent a small fortune on Koni FDS shocks for my Chevy Express-based "B" from shockwarehouse. My thinking was I wanted to get the best shock the first time and figure with my limited use, they would be the last shocks I would buy.
I bought the Koni's over Bilsteins specifically because they were NOT gas charged. They promised good ride and good control and do not disappoint. However, you'll enjoy improvements from any new shocks since our old ones are always worn more than we realize.