[oil pan 4]

If you want to talk about something that will actually increase fuel economy a noticeable amount then you need lean burn. When I went lean burn on my 454 I saw between a 10% and 20% increase in fuel economy.
Lean burn works.

The water pump uses hardly any brake horsepower at normal cruise speed.
The coolant pump doesn't use 2 or 3 horsepower it uses more like 1/6th to 1/2 horsepower.
The power the coolant pump uses is actually needed while the engine is running.
They only time the coolant pump uses 2 or 3 horsepower is at 5,000+rpm when pump flow is stalled and the impeller is cavitating like crazy.

Something you don't need running the entire time while rolling down the highway is the power steering pump.
It uses up to 1hp even during normal cruise speeds.

Removing a 1hp load will reduce fuel consumption by about 1 gallon over 12 hours of driving. To quantify to to MPG if you had a vehicle that gets 20MPG at 60mph. You would be burning 18 pounds of fuel per hour or getting 3.33 miles per pound of fuel. Saving 1 horsepower would reduce that to 17.5lb/hr or 3.43 miles per pound. Multiply your miles per pound to your chosen volume, a gallon of gas weighs 6lb.
Before saving one hp you got 3.33 miles per pound, times 6 pounds, for 19.98mpg.
After saving 1hp you got 3.43 miles per pound, 6 pounds per gallon for a total of
20.58MPG.
So removing the power steering load you could notice at the pump.
Removing the 1/2 coolant pump load completely at most you would see a 0.25mpg increase if you started at 20mpg. If the coolant pump load were close to 1/6hp which i belive it is, then it would increase fuel economy by close to 0.1MPG.

This is why removing the belt driven coolant pump isn't even noticed and why I don't recommend an electric swap for improving fuel economy.
Unless it's part of an engine off coolant circulating warm up mod.