I've read lots of threads on people lowering their cars and making handling improvements, but nowhere have I heard mention of upgrading the springs to handle more weight. I have a customer that is planning a trip to Baja and is going to be carrying a considerable amount of fuel with him. So far the idea's we've explored are:
1) some type of overload or air shocks
2) Having a heavier set of springs made
3) Possible swapping some springs from another body (126)
4) Fitment of self leveling system from a wagon (or 126)

The main issue is time, he is leaving in a few weeks, so we don't have much engineering time. Any ideas you may have are greatly appreciated.

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1987 300TD Turbo 5-spd
1991 350 SD Turbo (Frankenstein 603.970 crank, rods and head on a .50 bored 603.963 block )
1982 300D euro 617.951, 4-spd
2003 E500

2000 GMC C2500 6.5 TD (Double ott, ex DOT truck)
1980 Scout Traveller SD33T (Resting!)
1997 GMC K2500 Burban 6.5 TD (mid engine rebuild)