I've never heard of performance sway bars for a 123 car. If you do manage to find a heavier bar for the front, you'll want to also put a heavier one in the rear. I've gone through this before on other cars, they need to work together, if you stiffen one end, you REALLY need to stiffen the other to keep from building an oversteering or understeering monster.
The 123 cars are great in many ways, but from a drivers perspective, handling is probably it's worst trait. If you want to have a Benz that handles, I think you'll be wasting your effort on the 123 chassis. There are other Benz chassis that would respond much better to your efforts.
Sorry to be negative on your project, but it's just my $0.02.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in