Sean Hyland Motorsports recommends the TR6 for naturally aspirated modulars. That is what I run and they perform well. Sean Hyland recommends plug gap be set to .030 for boosted applications and .035 for NA.
The TR6s are one heat range colder than stock. On NA I would only use those if I built a block with high compression. I went to Auto Zone and purchased them today and they are running pretty good soo far. Got rid of the old platinum FMC plugs!! This car is running great!!
squeak93,
You are correct it is small! Sean Hyland recommends this however indicating "any minor power gains to be had from a larger gap are not worth the risk of detonation that may result". I am paraphrasing here but that is pretty much what he wrote in his book regarding high performance modular engines. Maybe you would pick up a few horsepower, but if you got a bad batch of fuel or something then the risk for blowing an engine is not a risk that I would be willing to take. The TR6 is also a colder plug, so the gap may need to be smaller to get a better burn than the hotter stock plug.