I looked around a little bit and I couldn't find anywhere that Ford Racing states not to use synthetic. I found they state that it uses Mercon Fluid or Dextron 3.

I do see that eaton does say that they don't recommend synthetic so I am going to contact them about it to see what they say.

None of these posts stated that conventional oil is not an acceptable fluid, they state that synthetic outperforms conventional oil. There is no reason that synthetic oil would not do just as good or better than conventional in your engine.