You need an adjustable vacuum modulator to adjust part-throttle shifts.  The adjustment is done with a small flat-blade screwdriver.  You take off the vacuum hose and inside the modulator vacuum connection is the adjustment.
You need a governor recalibration kit to adjust the WOT shift points.  Obviously, adjusting this will affect the part-throttle shift points as well, but the vacuum modulator gives you full control over both.