Squirt a little oil on the pivot points for the pedal linkage, particularly the two loops on top of the bellhousing, and work the pedal several times with the battery disconnected. Also be sure the return spring is there and in good condition. Stuck switch contacts by themselves would keep the armature turning, but the starter drive gear should have disengaged from the flywheel if the linkage was not in a bind. Sagging motor mounts and/or cab mounts can also cause the starter linkage to bind on the body metal.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!