if that doesnt work any resonable machine shop will drill a spark plug out for about 20 bucks per plug!

Good luck!

 

thanks everyone for all the advice. the issue isn't removing the plug, all the others came out just fine, the issue is being able to even get the 5/8 on the nut itself. i was hoping for a product that would break down the rust enough to just get the socket on, and hopefully something that wouldn't hurt if a little make its way into the chamber.

 

I had a similar issue on my 5.9. 3 days in a row when I got home from work, I hit it with PB blaster while it was hot (so it would suck in better). Each time I used an air blower to blow out what I could before soaking it again. I also used a long thin flat tip screwdriver to chip away what I could. After the 3rd day, I let it cool down, and didn't have a problem.

 

Did you try a metric socket that would be a hair larger?