I ended up replacing the right side cat with the part from my local dealer. The list price was $626.75 and with my good discount it was less than the aftermarket one. Furtheremore it is a perfect drop in part. Thanks for your detailed information.

BTW, the smog only place I go to just glances under the hood, connects the OBDII to verify monitors and does a tail pipe emissions analysis at two speeds. Easy enough to pass and charges $40.

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1972 450SL
1982 300D Turbo