Chevrolet Monte Carlo SS Part Number Diagram (Rear)
05934240 - Cover Cushion / Rear Bumper Lower Strip
OEM Part Number - 05934240
A replacement part for this is available via Dixie Restoration Depot, part # DM20257 SS
Trunk Lock Cylinder
The 83-88 SS Door & Trunk Lock Cylinder Set is available via Dixie Restoration Depot Part # DM30051.
The 78-88 Trunk Latch is also available Part # DM20073
License Plate Pocket - 20521258
OEM Part Number - 20521258
As far as I know, this part is not supported by aftermarket suppliers. Check Ebay, local junkyards, and other Monte Carlo G-Body vehicles. At various times, you may be able to find them on MikesMontes or GbodyParts.
The lens set can be found on Dixie Restoration Depot, Part # DM20036 and other vendors.