727 trans shifts too hard

There are three basic pressures in the VB, and some of them fight each other, and some combine . The three are called line pressure, throttle pressure, and governor pressure.
The line pressure sets the stage to make the guts take abuse, affects shift quality and opposes governor pressure.. Cranking the pressure up causes increased holding power for the clutches and bands. A side effect is harsher and later,shifts
The throttle pressure augments the line pressure to shuffle the shift from early to late, and makes the shifts slightly harsher with later shifts. Or actually if you set it up right, reduces the harshness to make normal driving bearable.
When the driveshaft is turning, the governor pressure is always fighting the other two, trying to accomplish a shift.The governor pressure is much affected by driveshaft rpm. That means 4.10 will command a shift much sooner than 2.76s. To counter this, there are several different flyweights available to get this tuned up.
The upshot of all this is Line pressure sets the stage, and the TP modifies it with the gas pedal.
So TB has it right, crank the T-P down, and see if it is more bearable.
As for me, I would get inside and reduce line pressure a tad, plus experiment with accumulator springs. If the shifts become too early, I would reduce the governor flyweight mass, or experiment with the little spring inside it. This, however is very time consuming. And not any fun at all to do in your driveway. So backing off the TP via the KD link is always #1,I guess.
Also the KD link at the carb should have a spring on it such that the link follows the throttle butterflies. This will reduce TV pressure directly with the gaspedal. If the link is allowed to float, sometimes it runs late and the pressure stays high.And then automatic downshifts are harsher than they need to be.

To make line pressures easy to adjust, I drilled and tapped the tranny case in just the right spot to insert the correct sized allen wrench. Now It's a 10 minute deal and most of that time is spent backing up the rear end onto a curb, so the oil moves to the passenger side, and so I can get under the beast.lol