ignition switch help - truck wont shut off

[hollywood68]

So the other day I pull in the garage and turn the key, pull it out of the ignition and open the door....then I realize the truck is still running. Luckily its a manual so killing it isnt difficult, but obviously not right.

Some background. This started about a week ago, sometimes it wont shut off and sometimes it shuts off normally. When the key is on the "off" position the tach goes nuts and it runs rough. Like most vehicles of this age the wiring has been messed with, but after inspecting the ignition wiring everything looks clean with solid connections. The truck does have HEI.

Electrical is my serious weakpoint, anyone have any suggestions? I am thinking replace the ignition switch and go from there....

I searched but could not find anything pertaining to this particular problem

thanks for any advice