Those hard lines will be as corroded inside as the tank is...trust me...
Various online suppliers carry them and the prices are minimal...compared to leaving them and continuing to have residue issues for ever....there is also a small length of rubber hose under the cab that you should replace..
Just drain the tank thru the sender unit hole with a flex hose...spray the back of the lower tank bolts with PB Blaster to make them easier to remove...
Then gently pull the lines out of the way as you and a friend lift out the tank...
Clean out the junk and dirt, paint the back wall of the cab in bed liner black...after checking the corners for rust...and yes there will be rust...
Replace the body seal for the filler tube,,,use liquid soap to slip the filler tube in easily when re-assembling...
Have fun young man
