Ok here is what I did, hopefully it won't take you a combine total of about 5 hours to complete as it took me because of multiple trips to the hardware store.
NOTE: this was done on a 240, but is only slightly different, so it still applies.

you need to drop the exhaust in order to do this, not right away, but you will eventually. these instructions apply if you cannot separate the rear exahust from the cat. if you can you only need to drop 1/2 the exahaust, but dont' try to separate these parts for too long, if it is stuck, it is stuck.

also, you need new gaskets for the header and the cat. you should not any may not be able to re-use your old ones.

1. securely jack up your car, having a hydraulic jack for the headers is helpfull.
2. loosen up the 3 nuts attaching the header pipe to the ex. man. but do not remove completely.
3. undo the rubber hangars for the 1st muffler.
4. place a jack (hydraulic) under the bottom of the headers with a small board between it and the pipe, get it firm as not to jack up the headers.
5. remove the 3 nuts for the headers and slightly lower your jack, then separate the headers from the ex man. with a pry tool, flathead or a pry bar. it shouldn't take much force to do this, but it does depend on how rusty things are.
6. remove the rear rubber hangers for the rear muffler, then lower your jack under the headers.
7. slide the whole exhuast out from under the car so you can work on it, this may take some manuvering because of the rear axle.

NOW the fun part.
take a hacksaw or some type of metal cutting tool (i used a dremel because that was what I had) and separate the cat from the header. the bolts that are in there most likely cannot be removed with a wrench as the heads are rounded. I dont' know why this is. Mine were, but yours may be different, if you can get a wrench on them go that route.

Once you have the cat and headers separated you need metal bits to drill holes through the cat. start with a small size to center the hole and work your way up to about 5/8" bolt. get 3-5/8" nuts and bolts from your local hardware store, attach (with new gasket of course) and reinstall. I tightened everything snug, then about another 1/3rd turn just to seal it well.

The part that is most time consuming is the drilling of holes, bentley talks about this, but it is kinda hidden, well at least I didn't see it when I read about it before I started the job. If you have everything ready with no trips to make to the store, you should have this done in about 3 hours or so.

Good luck
chuck
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'88 244 174K, '87 BMW 325e 180K (used to feed a '84 245, '84 244, '85 744)