What would you do? auto trans question

OK, I've had problems with my 727 not having kickdown, and the shift points won't change with adjusting the throttle pressure. Yes, the throttle pressure lever is all the way back when the gas pedal is floored. Did the air pressure tests, and the only thing I noticed was the front servo didn't hold air pressure like the rear servo did. Took the trans to a large transmission shop to have it rebuilt. They say there's nothing wrong with the trans. Was told they would try a new valve body. Then they say they don't have one for that particular year. They want me to re install the trans, and if it doesn't work, bring it to them.
questions: Should the front servo hold air pressure with an air test?
I thought other than valving, all valve bodies were the same?
Would you re install this trans without knowing what the issue is?
I'm not young, and I don't have the energy to keep pulling, and installing transmissions. Thanks.