So last week my cat started to rattle and I decided to just pop in a new cat. With little effort I got the cat to unbolt and come apart. (1990 240 DL wagon)

Now it seems the hard part is finding a replacement cat.

I purchased a new cat from IPD with a swivel flage, and after it arrived I realized they sent me one with a flat flare.

But the cat that came off the car has a flare that opens for a seal ring. In fact, I bought a new seal ring thinking that the new cat is the same style.

It seems that IPD catalog only mentions a seal ring for early 80's turbo, whose cats cost nearly 500 bucks.

Looking at the parts, I am beginning to feel that I can mount the flat flare of my new cat to the open flare on the down-pipe with a flat gasket.

What do you think? Is this workable? I talked to some people at performancemotorcars.com, and they think I need to replace the down pipe, because the current flage is superceded by the flat flange. Replacing the downpipe (from exhaust manifold to cat) is expensive and probably a pain in the ass.

Flat to flat with a gasket may work, but my only thought is that the proper join will allow the cat to be angled correctly so that the pipework downstream will line up. You can only try it and see. But if there is any strain in the pipes to make them align then something will fracture later.