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 300D Turbo 5-speed
1991 350 SD Turbo (Frankenstein)
1957 180D (Betsy)
1976 300D (best trade ever!)
1980 IH Traveller SD33T (Resting!)
1996 F-250 Powerstroke