NGKs are the easiest to read, Autolites not so much. Seeing the glaze on the porcelin those plugs overheated & are junk, trash them & go 1 step colder.
I agree, I see some gray/silver flecs on them and if that's the case it's been detonating. You may need to go more than one step colder or use better fuel.
I'm using NGK race plugs in mine but have also used Bosch and Champion with good results. What I did find is the heat range needs to be correct. Use the coldest plug you can and have it still run well. I would keep going colder one step at a time until it doesn't run well anymore.
The other advice in this thread is good, such as an MSD and leaning out the idle circuit a little.