Thanks for responding Aaron! I may have worded that a little poorly. I wasn't trying to imply that a special plug is required, just what would be the equivilent to the TR6. The TR6 is a tapered seat with .708 inch reach. I had some TR55 plugs sitting there and tried them just to see about the reach and it left them up in the threads a good way still. The plugs I ended up getting are NGK ZFR6F-11. These are a gasket style plug with 14mm threads, .750 reach, 6 heat range, v-groove design, and the specified gap for these plugs is .044. Sorry about the confusion Aaron!!