Fix for a 79 rear suspension
 

Ill make this quick so here it goes ,buy five hemorrhoid donuts and install two on each coil spring in the rear, the fifth one youll want to install on the front seat ,cause your going to need it. This is not a fix just a horrable joke.
I have not found any reasonable fix yet ,other than the expensive one.

Looking into the easy fix and may have found it!
 

There called spring stiffner adjusters, this will bring up the coil to normal heigth , they look a whole lot safer than the ones that losely ride on the spring.Next im looking into an air shock that may work , needs a few rubber bushings added and it may work. Keep you updated.

I have no idea what car your are talking about so I can't really help you.

But, replacing all the rubber bushings is a good start, they are old and shot. The only real fix is new rear springs. They are not very expensive or hard to change you just need the right spring compressor.

OK ,ORIELLYS says they have located a kit
 

Asked The Counter Help At An O'reilleys Auto Supply Store Here In The Houston Area, Cant Tell Me What The Kit Comes With , I Have To Purchase It First ,wait Two Weeks For Delivery And Then Investigate By Sight If It Has Everything I Need To Convert My 79 300 Td Wagon From The Sls Rear Suspension To A Regular Strut System.says I Can Return It If Its Not What Im Looking For But Needs To Have The Money Up Front For Special Order Items Like This Kit.cost ($375) .the Stores Phone # Is 281-367-1767 Talk To Doyle.

Now theirs a good deal whats wrong with your SLS? You could probably fix it the right way for $400.

strut
 

One H strut cost that ,this provides all new struts in the rear