catalytic converters

Hi all need to replace the cats on my 2001 4.0 p38. been looking and some places say only suitable upto a certain chassis number. Is there any difference in cats for either gems or thor? Apart from the price difference!! Cheers in advance guys

Have a check by looking underneath the car but I think you'll need the later set of front pipes, with the 4 O2 sensor fittings ( only the 2 front fittings are used but these pipes have another fitting to the rear of each cat), ours is a 99 and it needs these ones. They are about, for differing amounts of money..... there's also a few on ebay.