Indeed.... the 98s often have a b@st@rd inlet on the muffler: One clamped, one flanged. You'll have a lot of fun trying to adapt the muffler inlets without a flanger.
I had a muffler shop do my install. (50 series Perf/SUV) They installed a flange on the one inlet, cut the bracket that holds the pipes from the cats to spread them out a bit, welded the new muffler to the old hanger, then stretched an adapter to neck the outlet back down to the OEM tailpipe. Length-wise, it was a perfect fit with the adapter for the OEM tailpipe.
Also, if you're bending new pipes from the muffler back, INSTALL A RESONATOR!!! Without it, you'll get a drone on the freeway. The general consensus from those of us that have re-used the OEM tailpipe, or bent custom ones is that if you use a resonator, you are FAR less likely to have any droning issues.
FWIW, on the stock pipe, I get a *slight* drone at 80-82. As long as I stay under 80 or above 82, it's not much louder than stock, and I can barely hear it over the road and wind noise.
-Joe