The yoke is hard to get calipers on, but today I measured It. It appears it’s right around 1.7” diameter on the seal surface. Outside tube. Whatever you want to call it. A 904 would be smaller I think even if the seal would fit in this tailshaft.
If the yoke was off much I would expect some bad vibration. Keep checking the vent and such as frothy lube tells you something. You had already mentioned that it seem to fit as expected with little slop.
