727 3rd gear feels more like a down shift

What happens if you step on the gas pedal?
Make sure;
this is not due to a faulty low-speed circuit,
or that the powervalve is not dumping fuel in response to low manifold vacuum,
or, if you're running the Vcan on manifold vacuum instead of ported, that the timing isn't dropping out.
All of these can reduce engine power when you don't expect it,and thus,slow the car.
Then make sure that the manual valve inside the VB is seeing what the shifter is calling for. IE synchronize the shifter to the manual valve.
So once those are eliminated, then you can look to shift overlap.
In a 727, on the 2-3 shift,there isn't supposed to be hardly any, cuz the same hydraulic circuit that engages the Direct clutch, simultaneously disengages the Second-gear band. If you've eliminated the above,then, it sounds like your trans may have a hydraulic issue.
Just to help indicate how things are; what are your trap speed and car weight?
Is this really your first post since joining, in April/2016?