What would cause a loud squeeling in a 79 full size upon turning the wheel? It has power steering fluid

 

Have you checked the tire pressure? If that's okay, and you have the correct fluid level, you may have a power steering pump going out.

 

I did a check and one of the lead pipes has a bit of a kink in it...how likely would it be that that could be the cause of the problem?

 

Weak pump or worn steering box. Is the power steering fluid burnt looking? If it is, that is a sign that the pump is spent.

 

yes, the fluid is very black

 

Sounds like you are atleast looking at a new pump and I would recommend new pressure and return lines to the steering gear box. When you do this, make sure you bleed the system out appropriately by cycling the steering back and forth atleast 20 times with the front wheels off the ground, engine off. Then repeat with the engine running, adding fluid as necessary.