1968:
J-11Y 2642913
J-13Y 2642475
J-14Y 2444870

1970:
Same numbers for Champion plugs, but they also had Chrysler brand spark plugs. Let me know if you want those part numbers.

Bob

AAR 4-speed 3.91, Tor-Red;
70 440 6 pack Roadrunner 4-speed 3.54, Plum Crazy;
68 Formula S conv 383 4-speed 3.23, Electric Blue;
69 Barracuda conv Slant 6 OD4 2.94, 71 B5 Blue;
78 Lil' Red Truck, Red;
70 Challenger S/E. 505 6 pack, Passon 5-speed, 3.55, B7 Blue