From what I understand, it will fit. Several roadster owners discussed it in this thread:
Nismo OEM exhaust compared to aftermarket...
I had an OEM Nismo CBE on my Touring Z for several years. According to Nissan it is responsible for about 50% of the power gains on the Nismo Z, which equates to about 9hp. Although a little throatier then the base exhaust, it doesn't really add much growl. The difference is a little noticeable at start up and under full throttle, but its very tame under normal driving conditions.
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~Rob
-DD Air Guide, Stillen G3 CAIs, 63mm Throttle Bodies, Motordyne M370, Berk HFCs, FI TDX CBE (non-res, CF), Sprint booster v3, Ecutek Dyno Tuned, and the list goes on...