i have a 68' 400,points dist. the manual list an ac 43s plug but i can only find an ac r43s. it's a resistor type, i guess. what's the diffence? should i keep looking? also, i've pulled out a bosch super r6 10 871. they have a whiteiss or gray look to the ground, are they running hot. 6 mounths ago they were a light brown. no major timing changes but i am running it with 112 mixed in to get about 98 octain all the time now. nothing else looks off on the plugs. thanks tim