Scott B.
SE Expedition Society
Well depending on what kind of driving you do with your truck, you really only have a few options;
1. Add preloadable air shocks ( will add a little pay load capacity when you need it, and will not lose any flex.
2. Get stiffer leaf springs, like those offered by Deaver (unloaded ride will suffer greatly)
3. install helper air bags ( loses some flex but is almost infinitely adjustable)
All of which would work well, but if you do a lot of off camber flexed driving, air bags may not be the best choice.
If I were to increase my pay load a lot, I would probably go with a little stiffer leaf, and add air shocks .
My dad had a 1980 parisienne brome that used-to tow a 21 foot house trailer, and that's all that was done to it, air shocks in back.
Not intending to be a jerk or start an internet war, but...
The ride quality comment in number 2 is absolutely not true. I have a set of custom made Deaver's on the rear of my '93, and they ride/handle great. Best of all, they flex great when off-road.
To get the proper springs, you will need to determine the weight of your truck, the amount of lift wanted (and in my case, a snail wrap for the V8 torque, and inverted spring hangers). Deaver will build the springs to your truck/specifications.
As to the other points, if you plan to off-road your truck, neither solution is really compatible with maximum flex.