I guess it depends what kind of power your 440 has and how you are going to drive it. I have used 23 spline four speeds in the passed with no problems. I bought 67 hemi coronet years ago that didn't have a #'s matching trans, well, when I took it out it was a 23 spline unit. I replaced it with an 18 spline thans, but it held up with the 23 spline piece for a long time.