Hi, Warren.
It will fit but please note the following points.
1. Front heatshield
The heatshield at the front header will hit the A/C compressor bracket so you will need to trim off tiny potion of it.
The heatshield at the rear bank will fit without trimming it but you are going to have fun installing it with
lots of head scratching moments due to the limited space.
2. Rear sway/anti-roll bar
Depending on your suspension setup and if you are using the OEM anti-roll bar that came on your NA1 model, the bottom half of the heatshield at the rear CAT may hit the anti-roll bar at full droop.
Once the car is on the ground, there will be enough clearance.
You can either replace the anti-roll bar to NA2 style, replace it with aftermarket NA2 style or simply not install the bottom half of the rear CAT heatshield.
If you have aftermarket coilover kit or suspension setup, you may not need to do anything.
3. O2 sensor cable
As others mentioned, you will need to extend the O2 sensor cable.
However, you can install the existing front one at the rear header without extending it and just extend the existing rear one when installing it at the front header.
If you are buying the sensor extension cable, normally it will come as a set of two so not much saving.....
Also, as mentioned in #6 later, if you are replacing the O2 sensor, you better calculate the cost of new O2 sensors with the cable length designed for NA2 layout (no extention required) against the new O2 sensor with NA1 cable length + the cost for the extension loom.
4. Exh port gasket
Although the work shop manual states to replace this, you can re-use the NA1 gasket if it is not damaged.
However, while in there, I recommend replacing it to the NA2 one.
The port diameter of the NA2 gasket is slightly larger than the one on the NA1 type.
I have touched on this in my post #295 in the following link to NSXCB site;
Header Installation
5. Exh port nut
There are 7 nuts used at each bank when fixing the header to the engine.
While you can re-use your existing ones, you may want to use the one for NA2 model.
It has better treatment than NA1 model and will prevent corrosion for longer period.
6. O2 sensor
While you can re-use your existing ones, you may want to consider replacing them if you have covered about 60K miles even they were not faulty.
While it is easy to replace the one at the front bank, you could experience big time replacing the rear one later.
If replacing the sensors, please note the comment on the cost described in #3 above.
Good luck.
Kaz
