Personally I run only Motorcraft or Autolite plugs in all of my old stuff and have been for over 30yrs & am very very pleased w/them.
I get the best mileage and the best use out of them then any other plug I have tried.
I will NEVER us AC or Champion in anything old I own because of the poor workmanship I have seen in them such as Electrodes off centered, Electrodes either too deep in or to far out & have even had the ceramic break off when installing or removing them.
Now if it is a late model car/truck I install I will install a factory type plug regardless of the make of the plug. I learn that lesson years ago & found that if I used anything else they didn't last but a year or so...joe