Turns out it's pretty common due to the design. Pics below are not of mine, mine has no rust, being a California truck.
I was bummed, however, that there were no parts fiches available online. Turns out that may be 100% due to Toyota limiting access. How unfortunate that's their position. See the December 2009 note here
The resistor wire wears through after years of wear as gas sloshes around in the tank:
I thought I could fix mine. Bzzzzt. It was even more hacked than the one above.
Looks like I need a part # 83320‑39735, which appears to be dealer-only. Since it's Sunday, looks like I'll be leaving the truck sitting until the part comes in since I'd rather not R&R the tank again.
|83320||GAGE ASSY, FUEL SENDER|
|83320‑39735||RN61..SRT, FUEL TANK:65LITER||1||$97.85|
If this part is not available (bites knuckles), I may have to figure one out.
The resistance of a Toyota sending unit is 3 plus 2 or minus 3 ohms (full) to 110 plus or minus 7.7 ohms (empty). Basically any ohmic readings from 0 to 117.7 ohms (full to empty) on a Toyota sending unit are within spec.