Packard service literature in the early 1930's recommends AC spark plugs---  type K9, K10 or K12 for my 1932, depending on the heat range.   I've yet to find a list of what the modern designation for these plugs would be.  These are 14 mm plugs but what's important is the heat range ---   K9 is cooler, K12 is hotter --- and especially the reach into the cylinder.    I'd like some NOS plugs.  Nothing much on eBay. . . .   Any suggestions? --Scott