Hey-
Why not just use a EFI tank and route the high pressure line directly into your primary tank. This is the most simple way. No external pumps and everything is factory Toyota. When you are low on fuel, just hit a switch and watch your gauge raise slowly. Use a new EFI sending unit that has the low level warning light, and wire that up to the light in your toggle switch or something. Then when that light comes on, you know you've only got about a gallon left in your reserve tank and you can turn the switch off..
