Technically it's federally illegal. Not sure how that works at the State level, but I'm almost positive it's one of those "can add too, but not take away" laws...TX can't say you can remove the cats when the feds say you have to have one. They may not have to look, or care, but they can't say you CAN remove emissions devices. Converters are just one that the EPA has specifically spelled out. If the vehicle had one, you can't remove it. And if it didn't come with one? You can't add one.
You'd only have one, and yes, unless it was a diesel, it came with one.
I've always wondered, since when it comes to emissions there is no "off-highway" exemption by the EPA, how any racing class that uses a production vehicle, is legal.