I need new spark plugs for my 454.I'm not into fancy, expensive spark plugs. I just want the plain jane ones. According to napaonline.com, I shoud use AC Delco R44T for heavy duty, or R45TS for light duty. Does heavy duty refer to tall deck big blocks? Or just the ones with less emissions controls? My 350 used R45TS. What's the difference and which would you recommend? I'll be doing both short trips or stop and go traffic and also long highway trips, and of course 6 hour sessions of offroading.