Someone like Kevin with more knowledge of the the tranny valving hydraulics than I have should chime in, but as I understand it, the tranny works off 3 different pressures, regulated line pressure from the pump, governor pressure from the speed dependent governor valve, and throttle valve pressure from the throttle cable. I suspect the o/d lockup is speed triggered by a combo of line pressure and governor pressure, and it bet a modification of the governor pressure is the only way to delay the o/d lockup, unless you mod (raise) the counterspring pressure on the o/d lockup valve itself. Fiddling with the governor may have unintended consequences, so I'd limit my work to the o/d valve.

I looked at the 92 V4W2 non electronic tranny hydraulic schematics, and I note that (I think the color codes are mislabeled on the converter locked diagram) there are two lockup valves. One is a trigger valve, and one is a relay valve. Under governor pressure, at approx 2200 output shaft rpms, the trigger valve allows regulated line pressure to the bottom of the relay valve, passing regulated pressure to the relay valve and closing the pressure dump, which applies pressure to the lockup clutch. The trigger valve has a counter spring, and raising the pressure on that spring should delay lockup. Lockup is supposed to occur at 2200 output shaft rpms, and unlock at 2100 output shaft rpms.