I would recommend staying away from true duals running str8 back from your dual cat setup. I installed one on my truck. 99 2500 4X4, 38' swampers w/8.5' of lift. The sound comming out of the rear was messed up. One side sounded ok the other sound awful. I tore that out and installed a flowmaster 2in 2out muffler.

I guess it would have worked if there was an H- pipe installed also to even out the gasses.

Justin