A normal mechanic doesnt give advise about things he doesnt know about.Like AUTOMATIC TRANSMISSIONS.
You see an automatic tranmission specialist with extensive experience in what he does best & with what he had exposure to.
To increase the stall speed you must have a reason not just to pull some majic rabbit of his hat.It has to suit your CAM BAND,when the cam or torque starts to kick in.Youll know this by your dyno sheet(this thing doesnt bull***t unlike the owners of a new motor with something to prove)
If your confused,just see a pro
Gregg