so i ordered my header, and I was looking through ebay for a cat to go with it. I came across this:

http://cgi.ebay.com/ebaymotors/Chevy-Cavalier-Catco-Catalytic-Cat-Converter_W0QQcmdZViewItemQQcategoryZ33629QQihZ019QQitemZ8072408395QQrdZ1QQsspagenameZWD1V

obviously, it will "fit" since it has to be welded on, but is this what will work with a header? i ordered a weapon R header..... is this a 2.25 inch header? it didnt mention it in the auction

i dont understand what your asking. but that cat will work like you said it has to be welded on but i would suggest you get one without the breather becuase i dont think our cats have breathers( but i could be wrong). the cat will be after the header, it will go engine-header -about 1.5' of pipe then the cat and then out the back

hope thats understandable

what would happen if i get one with a breather?

I would get the cat that does not have the breather on it, Cause thing could alway happen like check engine light codes could pop up, Just get the with out, the breather.