Driveline Vibration

Jack, I'm not sure what the exact lenght measurement would be for your driveshaft. As far as the spline into the transmission question is concerned, if the spline is inserted fully into the rear of the tranny, then pulled back approximately 3/4" to 1 1/4" you should be in the ballpark. If there's any more play than this, it could very well cause your vibration problem. And welcome to the board and the world of A Bodies. :)