If your Caprice is similar to the LeSabre of that vintage I once owned you
remove the whole tail light assembly by unscrewing those big black
"wingnuts" inside the trunk.  Do you have an arrangement like that?

To get to any hardware you need to move or remove all the trunk trim up
against the tail panel, not just the carpet.

First study the outside of the lens. If you don't see any screws on the
outside then they are on the inside.

Look underneath the car and look above the bumper between the back of
the tail light assembly & rear portion of the trunk body. There might be
a chance you'll see a twist out sockets for each bulb, but I doubt it
the majority of cars now aday the whole assembly has to be reomved via
the trunk.

I'm sure somebody with a Caprice out there will be answering your
question shortly.

Good Luck

     Harryface    
05 Park Avenue, 32,272
91 Bonneville LE  304,498        

sorry to take so long.  i have an 87 caprice.  to change the
tail-lights i undo the screws on top that look like they just hold some
chrome trim down.  they also hold the tail-light assembly.  there are 2
more screws towards the middle that might be for the backup lights.  i
don't want to try them in case i break something but you could.  for
sure the plastic wing-nuts that are a bit lower on the trunk wall don't
do anything i can tell.
...thehick