As I recall 1975 was the only year MB hung the cats right on the engine. Big disaster. Any slight richness in mixture and they would attempt to super nova. In 76 they went under the car. Since you car is no longer required to meet any requirements in Texas, I would suggest converting to a 1972 or 1973 exhaust system. You should be able to pick up manifolds and whatever you need at a wrecking yard. The prices should be reasonable, because there shouldn't be much demand for those items. The only demand for any parts from an SL of that vintage would be for sheetmetel parts for 380s and 560s and the doors can't even be used on 560s. You should be able to get engine and exhaust parts for cheap.

Good luck,
Peter

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