Go the extra step when you replace that crossmember, and raise the gas tank an inch or two. You will thank yourself later. I know the truck tanks don't hang down like the runner tanks but it would still be smart to raise it a little. You can use some spacers or something, with new nuts welded to them to raise the front. Then build the new mount higher in the rear.
Oh and replacing the crosmember is the easy way. If you were to try and weld to the old crossmember you would just burn right through it. Those factory crosmsmbers are(tinfoil) thinner than the frame.
My lines are mounted outside the frame and I have never ripped off a front brakeline.
