That looks like a very nice Cutlass. Your desire to return the exhaust to 100% stock with OE converter I certainly understand. Unfortunately, you are right about the difficulty in finding one. The early catalytic converters from the 1970's were extremely inefficient by today's standards and had a tendency to clog up from poor running feedback carburetors, age and mileage. The early cats had thousands and thousands of ceramic beads with the surface treated with platinum and palladium. When I worked at the Pontiac dealer, we removed the service plug, (freeze plug), from the converter body, beat on the converter with a rubber hammer and a strong vacuum cleaner attached to remove as many clogged-up beads as possible from them. Then you reversed the vacuum and blew in a fresh supply of beads and put the plug back in. That's how they were serviced.
It was expensive even back then, made a mess and by 1982, the process was pretty much ended as a much better design converter had been developed. So other than finding an NOS mid 1970's converter, your replacement will be the much better, lighter, less expensive and more efficient monolith style converter. They do look a little different and are smaller. A 50 state legal replacement will work better than the OE cat, gain you about 2 MPG on that Cutlass and about 10 HP.
In the 1970's a replacement OE converter was over $300.00. I can't imagine what a NOS one would be today? 2-3K? Let us know what you find.
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