Here's more info I just found on a Mopar forum, that corroborates what Topz says:
That's refreshing to hear; as it's been an ongoing poor excuse to remove CATs as opposed to properly tune for them.
CATs don’t commit suicide on their own, they get murdered by incorrect A/F ratios that are either too lean to too rich. Too lean, and the platinum-enhanced element overheats and melts the nickel that is used to furnace-braze the rolled up element to itself...and before you know it the element separates under exhaust pressure and breaks up causing some of its parts to exit the exhaust system. Or worse, get stuck further downstream causing a major blockage. Too rich simply puts too much unburned fuel into the element itself, and because they are designed to operate so hot they glow, they then catch on fire and melt. Again, blockage becomes a real concern. These are tune issues…not CAT issues.
The other thing that gets swept under the rug is that increases in engine output means there is significantly more latent heat produced by making that extra HP / TQ. Catalytic convertors have thermal ratings, in other words, they all have a maximum rating to process exhaust gases. So the solution when increasing horsepower and torque...is to increase the thermal handling capabilities of the catalytic convertors.
It's real simple...you buy bigger CATs to deal with bigger engines / more thermal output.
KOOKs (manufactured by Global Emissions Systems Inc. here in Canada) offers quality CATs and are thermally viable up to ~700HP, their GREEN version is good to upwards of 900HP (both are 300 cell/inch). They are not the only supplier, Vibrant btw is another good example manufacturer that offers high-performance CATs of various thermal capabilities - right over the counter. FWIW, I would not touch any of Magnaflow's CATs with a ten foot pole.
This is a link to a manufacturer of "racing" cats:
HJS FIA-Approved Motorsport Catalysts but I bet it would be a major job to rework one of these to a Z undercarriage.