What spark plug should I use?

Nissan recommends as do many of the list members: NGK B6ES

The BP6ES has the projected nose on the spark plug. These run cooler and are better for highway driving

Gap: 0.028".

As seen on the Roadster list...

Or use NGK BP6ET 

This is what they call a semi-surface discharge, 4-electrode plug. 

I used to use these on all the stuff I worked on. I had a set in my 280ZX turbo for way longer than I like to admit (longer than a couple years...oh the shame of it, I am a bad car parent) and put a lot more miles on them in that time than any spark plug should have to see. And when I recently took them out (not because they showed any signs of loss of performance but just because I felt like I should change them once in a while or risk the ridicule of my friends) they showed hardly any wear and looked ready for another 40k. In addition to the longevity of the 4-electrode design (four times as many sharp edges = four times the life) the semi-surface design unshrouds the spark and moves the spark nearer the center of the chamber. They will work in any engine that can use a BP6ES plug.