[Pyrotechnic]

You can tell by the transmission crossmember. If it's double hump and looks symetrical on both the driver and passenger side, then your truck didn't come with a catalytic converter. If it has a hump on the passenger side, but dips down and wraps around the outside of the frame on the drivers side, it's a catalytic converter crossmember.

I feel that the double hump crossmember makes the frame more rigid, because it attaches the same way on both side and has the upper support on both sides. Also maked true dual exhaust with long tube headers easy.