I thought the flow rate is the same between the supra and Walbro 255. I did the job myself, and you should be able to do it within a day by yourself. Just run the tank low so you don't have the extra weight of fuel to content with. (You can drain the tank via the plug at the bottom if need be) You can also run into problems pulling the filler line from the tank, from the engine bay. Some will come off easily others, not quite so. Another recommendation is to run higher gauge electrical wiring to the fuel pump as they do suck more power. The standard wiring is capable but heavy gauge wiring is recommended.
Bother fuel pumps should be easy to fit.
Good Luck!