[68c10owner]

You know, Ive been doing this for almost 30 years and I`ve always known the 700R4 to have a 27 spline input from 1981-1986 and 30 spline starting in 1987. Even my transmission friends who are GM techs of 30+years have told me this and the guy who built mine told me as well. I did a google search and saw several places that say 1984 was a mid year change to a 30 spline input. Looks as if I may have been wrong on the input spline count but there is still no reason to use a unit earlier than 1987 unless you already have it.