I have finally taken the time to generate 89 mox fuel rods and loaded (and tested) a reactor V with a set of fresh mox fuel rods to calculate how much output it can produce. And...I think I misunderstood the purpose of mox rods because they aren't putting out any more power than regular rods. /shrug

Anyway, at the absolute maximum a Reactor Type V can produce 3.21 cooling towers worth of power. Now, you'll probably never actually reach 3.21 cooling towers worth of output simply because it takes a while to produce enough plutonium to create a mox fuel rod to begin with, so if you're cycling them in as you produce them they'll deteriorate before they ever reach max power. Thus, a reasonable upper bound is probably 3 cooling towers per reactor type v.

This makes the ratio:

• 4 cooling towers per zeus turbine
  
• 3 cooling towers per reactor (or just over 3 to be safe)

Thus, here are the final two endgame setups that should work and be able to power anything short of the final stages of Ambition of the Cosmic:

• 16 Cooling Tower
  
• 4 Zeus Turbine
  
• 5 Reactor Type V

Or this setup, which pushes considerably closer to the limit so you might not be able to run all the reactors at 100%:

• 12 Cooling Tower
  
• 3 Zeus Turbine
  
• 4 Reactor Type V
  
  
  Here's an image of the 12-3-4 setup in action:
  https://i.imgur.com/tEeCFwW.jpg