Realistic estimate Please

I don't recall if the 66 has the ball and trunion front on the driveshaft or a regular yoke. But if it has a yoke and you had a 904 with the /6 before the 904 instead of the 727 will be a much easier install. Plus I think you have to massage the body seam in the trans tunnel to fit the 727. If it has the trunion you have two options. One is to find a v8 trunion style tranny, or two is to have a driveshaft made to remove the trunion end.