I wanted to take off my fuel tank to replace the sparkplug and the fuel line just would not come off. I took off the clamp, but it's still on there really tight on the carb. I have no clue if the fuel line has ever even been removed on this bike, the rear tire was stock and 25yo when I got it, so it wouldn't shock me.

What can I do? Obviously, the fuel line will need replaced no matter what I do to get it off. So, any reccomendations for a replacement would be appreciated. Otherwise, should I attempt to cut it off, or are there Penetrating fluids I may be able to loosen it up?

Do what Lancer said.

Old fuel lines get brittle and shrink and get stuck.  It seems that in less than a year the new fuel line is no longer flexible

Take a shark knife, razor blade or Xacto knife and cut a slit along the fuel line to allow the fuel line to get loose on the nipple.  Be careful not to gouge a line in the nipple - make several shallow cuts along the tubing and then use a screw driver to pry the tubing apart and break the line rather than cutting all the way through.

If you have a paint stripper make it hot, and the rubber gets more fexible.

But I would cut it, dump it and put a fress viton line on it.
With the current fuels, the fuel lines harden even faster than before.

And who wants to sit and fiddle when it's not convenient to do so, like whit replacing the sparkplug.

If you carry on as before, it won't be long before you need god in your life.Anyway it's better to meet up with him sooner rather than later. But it's a shame to make your life harder than it needs to be.

He is called on so many times while people can eazy do it themselfs.

He would also think it stupid if you used the old fuel line or didn't make a handy door out of those chrome decorative caps on the cylinder.

Revelation 3:20