The new GM starter my freind is useing is part# 10465385 witch does say can be used on a ls7 motor....we doubled checked.
The problem he is having is that after the car starts and he lets go of the key the starter keeps going for a few seconds. So i tried a .015 shim no change so i try a .030 shim and no change sooo for the hell of it i try a .060 shim and no change,,,,,,,,,,,,,,i give

Yes he took the starter off and let it hang there and turned the key and it stopped every time i let go of the key..........

Yes he has a new LS TCI flexplate.
No he is not useing the spacer behind the flexplate.
The Neil Chance converter has the longer snout and its in a th350.
Its in a foxbody Mustang so its the Ford ignition if that matters ?

 

Ignition switch sticking possibly?

 

take a meter and take a reading at the starter to see if power is taken away when key is released. If not then you can start tracking back from there. Measure voltage with starter in place since problem only seems to be present when starter is mounted.