how long is a spring plate to suit a 65 beetle ???

on my 67 it's approx 37cm from the centre of the torsion bar (cover) to the middle nut on the axle tube.
i don't know where the nut is in it's slot, what state the torsion bar rubbers are in and this was measured blind (ie by feel behind widened rim) so it is only an approx measurement.
hope this helps.