I just replaced the front springs on the '92 yesterday afternoon with Skyjacker Easyrides. I used the 0-1 inch lift springs. The truck sits level to slightly lower in the front. I now have about 2 inches of clearance between the spring and bump stop. Ride is MUCH improved!!! The truck has spent most of its life empty to lightly loaded. I do not think the rear springs have sagged much from new.
My truck has spent the vast majority of it's life in a desert climate in central Mexico. It is as rust free as you will find in an older truck! I didn't even use penetrating oil on most bolts! Everything unscrewed like it was still new! I used to live in Illinois and I know what a rusty truck is. If your truck has seen much road salt, plan to take everything apart with a torch and replace what you have to cut off.
To address the front bolt size issue, my truck uses the big 9/16 bolt ONLY on the front spring eye. The Skyjackers use 1/2 on both ends. In my case, things were not rusted and the springs were sagging only slightly. I took apart the springs and put the main leaf from the old springs on the new ones. Made it a direct bolt in.
My old main leaf was only 1/2 inch lower than the new one. With the new leafs under it, that would have made very little difference in the final height of the truck. There is a good spring shop down here not far from my house. I took the leafs to them and the re-arched both mains to match the new ones. They replaced the rubber bushings too. They did it while I waited... took all of 15 minutes! Price? $6. 00 American for everything! You have to love some things about this country!
I checked prices from several sources and they were all very close. Delivered to a friends house in the States, they cost $300-350 without bushings. Shipping was $50!
I recommend the Skyjackers! They made a NOTICEABLE difference in the ride!
Steve