Starting this instead of fouling up the Q&A thread more.

I'm confused as hell what to select when searching for a replacement high flow cat.

The 3.0 CL cat is longer than a 94-97 Accord cat (and presumably a 2.x CL?), but a 94-97 catback exhaust should fit the same, even though the Accord's pre-axle pipe is longer?

So does this mean I should just go with a 94-97 Accord length cat, since I would be going with a 94-97 Accord catback?

The 3.0 has larger diameter piping than the 94-97 Accord.
But this shouldn't matter if I'm going with aftermarket headers that have an outlet of 2.25" and an exhaust that has an inlet of 60mm.
(I've read elsewhere on the great internet that a 2.25" in/out cat has worked for others with 60mm piping. Please correct me if this is wrong.)

So what I have gathered is that I should use a 2.25" cat that is the length of a 94-97 Accord cat.
Does this sound right?
Will the headers change that? Will the catback exhaust change that?

Okay, so now I'm confused when looking at the length of cats in general.
Places have them in varying sizes, from 13" to 17", all of which claim to be direct replacements for the OEM cat.
Some of them are different depending on the 3.0 or the 2.x.
Some of them are different between the Accord and the CL.
Some of them are different between years.
Some of them are different depending on the brand (i.e., one brand selling the direct OEM replacement as one size, and another brand selling a direct OEM replacement as a totally different size.)

Am I really missing something here?

What the fuck length do I get??

 

Can you just jack the car up and measure it? That's the only real way to find out since it's probably not easily found using google.

Also, you're correct on the diameter. If the collector is 2.25", it's best to get a matching cat and exhaust. If that's not possible, you can buy step-up or step-down transition pieces on summit.com to help make the exhaust flow a little smoother. You'll just need to a muffler shop to remove the necessary flange and weld in the new piece.

Edit: Never mind the first part. I see now that the Accord exhaust might be longer.