What's wrong with the "Duck"?Google is your friend.
they are tapered & 1/2 inch thread. I have boxes of them. some are blue mopar some are red moparCan you provide a few pix of an individual plug not in the box or wrapper. It is likely that the plugs are 3/4" reach plugs for the 360 engine or possibly a latter 318. OR they may be 1/2" reach TAPER SEAT design for the later slant 6 engines. I cannot seem to find a cross reference with Champion or AC or NGK but my info is not current.
BOB RENTON