I show a 6" tail 350 at 27-11/16" while the 400 is 28-3/8". That is 11/16" difference. Depending on how long your driveshaft is now, you may bottom the yoke unless you shorten the shaft.
You will also need a 400 yoke as the diameter and splines are different.
The 350 has a cable for the downshift. The 400 requires an electric switch on the carb or gas pedal.
You will also need a 400 yoke as the diameter and splines are different.
The 350 has a cable for the downshift. The 400 requires an electric switch on the carb or gas pedal.