Starter Problems Continue.....Help!

[Huskerboy2]

When I start my one ton, the starter continues to crank even if I turn the key off. This used to just happen once in awhile, but now it is pretty much a constant thing. Initially, I changed out the ignition switch, hoping that was the problem and not the starter. I replaced the ignition switch with an NOS GM switch and when I went to fire it up, same problem. I had to disconnect the battery to get the starter to stop.

At that point, I figured the problem must be in the starter. I pulled the starter today and took it into NAPA. The guy at NAPA put it on the test bench and he says the starter works fine.

He was at a total loss, once the starter and ignition switch were ruled out. For some reason, the truck seems to continue to send power to the starter.

Any ideas out there? I'm stumped.