Going to a larger boost valve will increase clunk via higher pressure. V6 engine typically had smaller boost valve
The sonnax valve for over run applied in additional gears will increase clunk.
I suspect there is a problem in the drive line area if this clunk is as bad that you indicate.
i would keep the PWM lock up setup for the converter. If your programing has the converter clutch applied at lower speeds via PWM logic, you will not be happy with the on-off setup valve you mention Sonnax or TransGo. The vehicle will feel like it is dogging out as the converter clutch is applied fully, not slipping.
In the 1995 trans , it is simple to block the PWM valve and have the on - off feature. I would use the TransGo valve if you decide to move forward.
The Sonnax lock up valve for the pump is a fine addition, they work well.
Dont worry how old you are... it is the mileage on your body that adds up.