Well, I guess you don't want to drive a hole in your tank
What you could try is to get a cheap inline pump like you would use on an older model car (I think these can be had for $19.00 to $25.00 at any generic parts store) and plumb it into the fuel line along the frame..perhaps remove the fuel filter and attach the pump temporarily with a piece of hose, and use the cheapo pump hooked to your battery to pull the fuel out of the tank into a bucket or gas can. (keep everything on the ground to avoid static).
I think the fuel will flow through your old pump and as you are replacing it anyhow, you don't have to worry about hurting anything. Remember when you replace your pump to replace the strainer at the bottom and put in a new fuel filter while your at it.
The only other way I have done this is to use a good floor jack with a wide top on it to lower the full tank to the ground then after removing the sending unit drain the gas out through that hole.
Good luck