If your vehicle is going to be smog checked on a dynomometer (1999 & older vehicles) it is doubtful a smog check station will inspect the vehicle unless the tailpipe reaches the rear bumper of the vehicle (or some unobstructed location where it will not interfere with the dyno). It's not that a vehicle can not pass the smog check without a muffler. A muffler inspection is not part of the emissions test process, it is merely a safety factor in terms of testing, and a noise suppression issue for all other practical and legal purposes.
You might find a smog station that is willing to take the risk of attaching the smog probe at an unconventional location, but you'll probably have to visit a few places first.
