One for a 904. Every flexplate made by whomever usually states which trans it fits. It's that simple. Not to be a smartass, but What you've essentially done is try to fit a square block into a round hole
I can understand you. The thing is a initially order this plate
Hughes Engines
And it does not fit. As you note it states of fits 904 and 727. So therefore was under the impression there was no difference.
Now my engine has an eagle stroker crank with 6 bolt pattern and internal balance. To be used on a 904 trans. And quite frankly still can't find the correct flexplate