If it is on the column, it is probably linked to a steering wheel
lock.  But since you have an aftermarket floor shift either there's no
shift interlock or someone went to a LOT more trouble than your
average rod builder would.

I personally would just get a Stude ignition lock and put it in the
dash where it's supposed to be, and get either an earlier van column
or an Ididit column and lose the key on the column (actually I'd be
half tempted to make a Stude column work because IMHO a large diameter
column looks wrong in an older vehicle) but I doubt you're going to
want to go to that much trouble.

I really can't answer your other question; I can rekey German car
locks and that's about the extent of my experience.

nate

IIRC the lock cylinder pushes on a rod connected to the actual switch
further down the column. Perhaps the rod is binding up . If you can pull
the key half way out, the cylinder and/or key is worn.

Lee D. figured it out, a 30 second fix. The truck is now a floor
shift, with a column shift tilt column. The P.O. kept the shifter
collar, but filled the lever hole and the collar had slipped out of park
so the wheel would not lock.