Yes indeed, the 790 Thrux is a NBTZ and the 865 Thrux is NBZT. I'm running the NBTZ in my 790 America with good results. My seat-of-the-pants guess is that you should match the needle to your engine's displacement for best results. In Dave's big bore case I believe the NBZT will give the very best results.

A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)