Want to swap door striker plates...how do I access the back of the striker plates?

[DeadheadNM]

I want to add a set of Parkerized door striker plates to my Blazer. On a pickup there's a set of brackets on the backside you can easily access. Today I swapped my RH rear inside trim panel and was surprised I couldn't access the striker nuts/retainer plates. These are boxed in by the pillar. Do the plates bolt onto nutserts on the pillar? I'm afraid if I unbolt the plates the rear retainers will drop into the pillar.