I have been having really good luck with AC plugs lately. I also run a lot of Autolite 86s and I've still got some Champion RJ17YC in the rotation, got'em for $10 for a carton of 50 some years ago at the Winter Swap Meet in Denver. I use an extended tip spark plug whenever I can. My '64Dog uses so much oil that I am changing plugs often. I thought the super hot Champions were going to do the trick but they aren't any better and after a couple of cycles of cleaning have about a 30% failure rate. Bummer. The Autolites and the ACs work and will clean up and work again.
Tip: Put the dirty plugs in the oven at 550 or if you have a self-cleaning oven run them through a cycle, although I haven't tried that higher temp yet. I also found that soaking them in Ospho first aids the cleaning process.

Also, if you're willing to do the work there are usually many vintage new plugs on the 'bay.

R