Hoping that the gurus can 'splain this for me. Checking around various manufacturers websites, all the oil filters recommended for the 1969 Plus 8s (i.e. Purolator L30005) have a 13/16"-16 thread. My '69 +8 uses a 3/4"-16 thread (i.e. AC Delco PF2). What gives?

Tom Morris
1972 Plus 8
1932 Super Sport "Beetleback"
1961 Morris Minor Tourer
1972 Triumph T120V