Depending on your fuel reg setup, you could unhook the return and put that into a bucket/jerry can, then start the car and let it idle until it stalls. Hook the reg back up and put in 98 - easy as. Did it on my GTR when making the swap to E85 and it didnt take long at all. On a separate occasion did the same thing but used the ECU to turn fuel pumps on and didnt start the engine.
Putting a tube down the fuel filler to syphon the tank is damn hard with a GTR fuel neck and you wont get as much as the fuel pump will anyway. Food for thought