Catalytic Converter question
 

I have a 1999 318ti. My car's currently throwing CEL's for both the O2 sensors (upstream and downstream) and the Catalytic Converter. Since upstream O2 sensor failure can result in damage to the Cat, I'm going to assume that needs replacing alongside the O2 sensors, which are junked. 318ti's are rare here, and a new catalytic converter is expensive, so I was wondering - if I find a 318i at a junkyard, can I take the cat off that and put it on my car, since the engines are the same and so is most of the physical components?

Personally I would not use a 20 year old cat.
I've read elsewhere that Magnaflow cats work.
https://www.magnaflow.com/products?partNumber=94305
They look to be around $120.00.

2nd the Magnaflow.

I got mine about 3 years, and maybe 15k miles, ago and still going.

I didn't change my sensors either, don't remember the code I was pulling.