Hello Rudy,
As I recall, a Sundial B has a ball valve assembly on the bottom of the pickup tube, so you will need that as well. My old Sunny B is in a container behind a few tons of other stuff so will be a while before it sees daylight. Someone here may have pictures or dimensions they can supply.
Correct length should just allow the ball valve to sit a few millimeters above the bottom of the tank. Great little old motor you have there. Kind regards,
Combustor.