I'm that old. The trans has modulator and control pressure adjustments. The easy solution wil be some combination of earlier shift (control pressure linkage) or harder modulator pressure. The modulator adjustment is available after removing the banjo bolt. The 3 or 4 mm allen adjustment can be done through the hollow fitting into the modulator. Turn it a turn at a time clockwise for harder shifts.
I would do a little of both depending on the driving condition.
Bosch Master, ASE Master, L1
33 years MB technician