I have a 76 350 4bl that I had 97 Vortec heads installed on. The mechanic that installed heads/intake used NGK UR4 plugs (thats what the 76 350 used). Fast forward one year. All my plugs were beyond stuck and I broke one off attempting to get out. Is now fixed and all plugs loosened. I am going to replace the plugs with TR55's since everything I've searched leads me to believe the problem is the UR4's length was creating detonation right at the plug hole. All my boots are burnt/splitting right at the 90 bend. My question is, will using the 97 gap of .60 rather than the 76 gap of .45 make a difference?