Disconnect the fill neck and fill neck "vent tube" from the body side, since you can get to that easily. You'll need to bend the filler hose to get it to clear everything for the tank to drop, but it's no biggie. You can wedge a screwdriver in between the rubber hose and the fill neck to break the bond between the metal and rubber. Usually twisting the rubber hose will work to completely break it free. It may take some work.
It's also not a bad idea to jack the body up (leave tires on ground) so that you've got more room to work.
Don't forget to disconnect the black ground wire from the frame, and on the TBI stuff, you can disconnect both of the other wires at the weatherpack connector, so when the tank drops you don't break them.
I'm not into replacing those things, even though the K5 filler is fairly easy to find, it's still money you shouldn't need to spend, at least if you are cheap/thrifty like myself. /forums/images/graemlins/smile.gif
Once you get those off, get a floor jack or something, preferably with a piece of plywood on top so that it doesn't mar the tank. Position the jack so you can best get the straps to drop down from the rear of the truck. It will still be in the way, guaranteed, when the straps are undone, but at least it will keep tension off of the straps as you loosen them. Since the tank is almost empty, you will be able to manhandle it fairly easily.
Once you get the straps off, let the floor jack down slowly, until the tank is down a bit. Preferably with the front of the tank down, then go in from the front, and undo the lines. You'll need tubing wrenches, don't want to twist the fittings off.
Once those are off, then you can drop the tank all the way down.
I found it MUCH easier to deal with everything by removing the bumper, and if still present on your truck, that filler piece between the tailgate and bumper for sure. The nuts on the two straps are much easier to deal with that way.
