I'd try running power direct from battery to wiper motor to see if it works that way before swapping it.
Got a heater core ordered for the 90, so hopefully get that changed next weekend. Gonna be cheap and just fill the rad with vinegar or clr for a couple days and flush it out, and hope it doesn't develop any leaks.
Filled the 4 runner with premium Shell fuel, no ethanol, and bumped up the timing some by ear. Still gutless, but it's definitely more responsive than it was. Nicer to drive now, requires less throttle to get up to speed. Hopefully mileage improves a little as well.