there's one for 26 spline and one for 30 (that also fits 727)
the 30 spine is 66-71 and is PN 2400300 (fits other stuff too)
the 26 spline is PN 2400163 and 2.25" OD (if you have a "706" tail shaft this is what you need)
and one for the 26 spline OD trans that's 2.375" OD (tail shaft 364 & 386)