Need tips about removing gas cap

[dmjlambert]

Well, if I had known this sort of thing could happen, I would not have put this gas cap on there. Last year I got a new gas tank, sender, and gas cap from Classic Industries. I ordered the gas tank from their catalog and the gas cap their tech support guy recommended. It is a locking Stant cap. I've been happy with it until today.

I went to put gas in the truck, and there is no way that cap is coming off. It is stuck on there so surely, you would be impressed. It certainly has made an impression on me.

It looks to me like it is not fitting evenly on the neck, I don't know how to describe it well, but here are pictures. I'm not sure if it was hit, but it doesn't look damaged. I am always careful to just gently press it in place, but I suppose something could have happened with neighborhood kids or somebody in a parking lot since a couple weeks ago when I got gas. The key turns with no problem, and I can't see any damage or problem with the cap, it just won't come off.

I just don't know what to do. I've done a substantial amount of cussing, but that got me nowhere. If I could destroy it somehow to remove it, without generating a spark or sending bits of metal down into the tank and without destroying the tank I guess that would be OK. Otherwise I guess I will need advice on how to cut the neck off of the gas tank safely, so I can replace tank and cap. OMG. Ideas?