I've been running K&B 1L plugs in most of my engines for quite a while, and they work just fine. I used to use the Fox Miracle, but I have no idea why I don't now. I'll have to get some to find out.

However, the K&B and Fox plugs are slightly longer than an OS 8. Not long enough to hurt anything, but I've seen some new OS FX engines that wouldn't run right with the longer, hotter plugs until broken in. Too much compression I guess.

There are lots of good plugs out there. OS are good, but expensive.