Is there a screen in the neck at the top of the tank. I tried to syphion out the fuel only getting a gallon or two. I need to remove the fuel to lower the tank to install a draw straw. If anyone has ideas let me know. Thanks stock659

 

There should be a "roll-over/anti-siphon" valve in the neck.
You might be better off disconnecting the filler tube from underneath the truck. (If your fuel level is low enough)

 

Just raise the bed on the tank side. I just did this recently to change out the fuel sending unit and found it easy to do with a bottle jack between the frame and the bed.