I posted this a while back... but i cleaned it up the other day for another forum. here is what i did on my 300SD. I'm sure all of this can be transfered to the W123. the 116 sway bar may need to come from a 115. but I'm sure it could work.
W126 suspension upgrades (the cheap and dirty way)
THE BACK
I've installed 3 Nub rubbers in the back, a rear sway bar off of a 116.
I read somewhere that the 116 sway bar fit in the 126... but I can't remember the forum, and i searched all over the place for verification, but no luck. so i went to the pick and pull and laid under a few cars. and it looked like it fit, except its mounted further back in the 116, thus the bar is about twice the diameter as the bar in the 126, to make up for the extra torque the longer arms would deliver. so i thought SWEET. I'll just lop off the extra 3 inches of arm, and drill some new holes....
I took the bar to school, and removed the 126 bar and tried to install the 116 bar. no luck. the 126 bar has a bend in it that moves it out of the way of the rear dif mount. this bend faces the rear of the car. well the 116 bar has a bend also, but since it is mounted further back in the car, the bend bends toward the front of the car to clear the spare tire sump in the trunk. so the only way to make the 116 bar fit was backward!
so i ran to home depot, and bought some steel bar stock. 1in x 1/4in x 3ft cut it into 2 14in peaces. i then cut the arms of the 116 bar off so that only 6 inches of the arms were left. i them welded the bar stock onto the 116 bar. i used a vice and the leverage of the 116 bar to bend the steel bar stock into the shape of the arms on the 126 bar and.... IT FITS!
it rubs on the spare tire sump. so i took a hammer to the sump... it needs a few more wacks. i had to use a razor knife to carve the 116 sway bar bushings to fit into the smaller 126 holders.
I'm currently using the plastic 126 sway bar links. but I'm going to order some metal ones off of a 115/116 to handle the stiffer bar better.
THE FRONT
First I started by chopping 1 360 degree coil out of some front springs i got from the pick and pull. I installed them and the car sat way lower. so low that the oil pan hit the ground and the tires hit the finders. I do have rather large tires on the car. 60/225/R15.. anyway. the car was to low and to soft for my taste. I also noticed that the car was leaning to the drivers side. so i compressed the springs and installed some coil in spring rubbers. this lifted the front of the car slightly and made it way stiffer. i also installed a 2 nub rubber on the front passenger side and left a 3 nub on the drivers side.
the car now sits great. and handles awesome.
the car still leans toward the drivers side. both front and rear are 1/2 inch lower on the drivers side. I plan on making some shims and shimming the drivers side until it matches the passengers side. but I'm waiting on that until i get new tires. because i'm sure part of the reason I've got a lean to the drivers side is because i'm in the car alone most of the time.
attached are some pics of the modified 116 sway bar. and the rubber coil shim i installed in the front. and the spring out of the car with the rubber coil installed in the spring. and the car in the parking lot outside.
