I have had good success with the projector nose NGK spark plugs. My choice being the NGK BP8HS, but my engine typically spends most of it's life working it's guts out.
Good advise has been given to make sure that an extended reach spark plug (like a projector nose design) doesn't hit the piston as it comes to top dead centre.
Make sure you install the plug with the piston well below top dead centre then manually turn the engine over slowly to see if there is any mechnical interference between plug and piston.
I have various designs (from different manufacturers) of billet cylinder heads and on two of them, i cannot use a projector nose plug due to interference problems, so i must use the "non" projector nose version.