With an aluminum head, make sure the engine is completely cool, maybe let it set overnight and change plugs in the morning. Try to spray some PB Blaster on the plug and let is soak in for a while and try again. If you can do without driving the truck for a few days, spray with PB a couple of times and really let it soak in good.

I had an old car that the spark plug was stuck and it ending up breaking the threads off in the head and the rest of the plug came out. I finally got the rest of it out with an easy out, but this is not what you want to do. Luckily the car had steel heads and it didn't mess anything up. Make sure to put some antiseize on the new plugs too.

Hope this helps,

Kevin