Sounds like you just have shifter issues. Give it a proper lube and that should correct the problem.

Linkage is no more the a single steel plate with a nylon bushing at each end requiring little to no lube.

The shifter itself however is much more involved, it pivots on a large bolt, they tend to seize up at that point when not used regularly.

Then sometimes what feels like it's moving correctly again is that bolt pivoting via the threaded end where it screws into the bracket, rather then the bolts shank where its supposed to.

Shifting to N or 4L requires the lever to move straight down first then back, a little roll pin clears the notch in the plate at the bottom of the shifter. Its not internal to the shifter so you can see it.

Gotta get a can of penetrate/lube of choice and spray the heck out of it carefully working it free again. Watch the head of the pivot bolt, make sure its not turning with the shifter.

The shaft where it moves up and down for 4L, its bushings are covered by rubber boots top and bottom, small zip ties maintain a water tight seal. Clip the zip tie at the top and spray inside it to free up that point, might have to work from the bottom too, be sure and replace the zip ties once its working freely again.

When you shift the gear shift into park and the truck is running it grinds like crazy TCs not in a gear so the trans is spinning with the motor, the park pin you hear grinding.

Oh wait you said 87, that ones different, you move the lever back to 4H and then left and back to get to N and 4L IIRC? Anyway look it over a minute you'll see what and where that part needs a lube job.