Can't speak for their plugs but their coils suck they do not last I have had several. I try to run AC in GM street motors. I have NGK in my race motor I may try AC next time. Need more details on the motor if its a dome piston motor you will need non project tip plugs if you have aftermarket heads they may have came with a recommendation to get you in the ball park as far as design and heat range goes. The NGKs in my 383 sbc are about 7 years old. I know I need to change them.