I thought I would close this thread with a couple of practical remarks - maybe someone will benefit from that.
As I wrote a couple of posts below - the new front exhaust from Mercedes is a perfect fit.
It runs fairly close to heat shields both on firewall and under the floor. If you chose or had to go for the solutions with clamps rather then weld - you may want to use type of clamps that are flat on the top. If you use e.g. 8mm loop rod type clamp - it will be very close to heat shield and may make noise. I found clamps (I had to go for this solution) that are steel solid band 1-2mm thick with 8mm bolt as tightener that work fine there.
Second point - in the clamp solution you need to weld in pipe pieces that will stick out of the connected length of the front pipes (I used cut pieces of pipes from SLS). Now, if you want to have the blow passage between the left and right exhaust pipe, you need to drill holes in those pipe pieces you weld in, otherwise their walls will block this passage. When you look at the pictures I attached to the previous posts, you will see what I mean.
I am not sure if, when you buy the middle piece original from Mercedes - the tips of the pipes from this middle piece go deep enough into the front piece to cover those passages and if so if they have holes in them. I would check that. My original middle piece was cut when the car was restored to make it fit to the remains of the old front piece that I know exchanged - I do not know how deep it was supposed to go into the front piece and if it had the holes for the passage.
