It doesn't really matter on a car with IRS. The exhaust is more or less flat other then the down pipe to the engine. From what I have seen MB has a down pipe section that goes from the turbo/exhaust manifold to just the rear of the transmission. then there is a flange. Then a second section that goes the rest of the car. The pipe is just bent so that it is in the right place when hung.

Most import cars are welded with flanges around different assemblies (down pipe, catalytic converter, down pipe, ect) Most domestic cars used different sections of pipe that are sleeved and clamped together. You'd think the welded and flanged exhaust systems would be harder to repair, but not really. The sleeve and clamped connections are clamped so tight, then rust, making it so you can't unsleeve them for service. This is why all exhaust shops weld, because they have to cut out sections of exhaust that will not come apart.

I bet your exhaust shop will weld as needed and will reuses the stock flanges and leave them in their current locations.

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