The two things that most affect the shift speed are control pressure (throttle link pressure), and governor pressure. Either a greater control pressure, or a lower governor pressure, will cause a shift at a higher speed.
Both the control pressure, and to a small extent the governor pressure, are also affected by the modulator pressure. Increasing the modulator pressure will cause the shifts to become firmer/sharper/harder, but until the shifts are too firm, an increase in modulator pressure will raise the shift speed. Before changing the modulator pressure, try increasing the control pressure by shortening the link from the throttle to the arm on the right front of the transmission. Shortening that link will also affect the 1-2, and 2-3, shift points.

With a 3.92 axle ratio the 3-4 shift would occur at 130KPH.