Realistic estimate Please

Rob, you 66 has a standard type tranny U-joint stsyem, not the old ball and trunion, so you're good to go on that one.

The 904 will be a much simpler and faster fit than the 727, although that will also work with a little more effort. The pinch weld seam in the tranny tunnel needs to be flattened in order to use the 727. The 727 also uses a different front tranny slide yoke than the 904, so you'd need that also to use the 727. What torque converter are you using - the old /6 one?

I'd count on Mr. Murphy coming for a visit and imposing his Law during the swap, so be prepared to spend the compete weekend on it. Good luck.