They mufflers are the same from 1985 to 2007. Make sure that all front head pipes and crossover tube clamp bolts are loose. Also, keep the muffler hanger bolts loose so that the muffler will pivot. install the rear pipes to the muffler first (only snug, not tight) than pivot the muffler all the way forward and fit the front head pipes into the muffler. Now fit the top the back head pipes to the round clamps and tighten to whole system up.
One more thing, the head pipes (x4) and crossover tube have steel mesh reinforced lead gaskets that can be easily deformed and cause exhaust leaks.
Good luck