Is the car an attempt at all out horse power and track performance? Are you trying to make money off the street raceing? If not, why bother? If you have the motovation for alot of work for maybe 5-10hp top end, well . . . your choice. If you live in an area that does not smog check, when they clog you could choose to eliminate them altogether. However the left side cat is welded to the exhaust manifold, so a gutting is logical. But alot of dirty nasty work to get the remains out of the pipe. If exhaust restriction is a major concern, go w/ headers and really open it up to breath!
Just my opinion.