The manifolds might be different between the '01's and '03's for example:
On one, the cats are part of the manifold, on the other, they are a separate piece...
so you can get the manifold onto the engine....but you'd need to rube goldberg the rest of the exhaust to match up.

_________________________
- TJ
2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....
Friends don't let friends drive stock.
http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif