I've sprayed it out with a pressure washer and the water started to come out clean then I filled it with Gass and next thing I knew the fuel turned a dark brown and had contaminants in it somone please help I can't find a replacement 

I did mine a few years back - tank was out of car for this messy task. I used the internet to get details and went for it - hydrochloric acid of some particular strength ADDING IT TO WATER ALREADY IN TANK as is the acid precautions list starting point. Forget how long I left it for, rinsed, rinsed and rinsed, then once happy with shiny insides, added more water and a heap of carb soda/bicarbonate of soda to neutralise any acidic stuff lurking and more rinse cycle. Dry out in the heat of the day. No more gunked fuel filter problems. White vinegar might be a safer option for you to try. I would suggest you experiment with rusty metal waste pieces first to see what happens.  As soon as white vinegar soak for 24 hrs is done, wash up and rust starts to form again quickly, so spray with penetrating oil to see how it protects things from oxidising. Move on to the tank when you have some experience. READ ALL PRECAUTIONS OF USING AND HANDLING ACID. PROTECT EYES !!

 

Ok thank you so much for the help 

You could take it to a radiator shop and see if they can clean it for you.