3 pin neutral saftey switch check?

On this particular van, I had problems before in a different transmission where the neutral saftey switch seemed faulty, so I bypassed it with a push button wired to momentarily make the connection to start the vehicle. After a few months of this, it was discovered when replacing the torque converter, it was discovered that when converting the transmission from a 5 to 3 pin switch using a Sonnex conversion, it simply was a matter of the adapter and or washer, not being screwed in or compressed enough to make the connection. Moving on to the 3rd transmission which required the same conversion when swapping a 2001 5 pin connector to 2000 3 pin connector harness, the van started correctly before I replaced the heads, which had me streching and moving the wiring harnesses repeatedly in the process, so I'm thinking of ruling out the switch and, moving on to the actual wiring and connections from beginning to end as 67Dart273 suggested.