Well I got the tail lights in last night and was able to start cleaning them up today. They look like they were stored in a garage for a very long time.
I took a gamble when I bought these due to the bad pictures and possibility of hidden damage but they turned out to be amazing. No cracks at all, even the bulbs are in good shape!
Luckily the grim wasn't thick, everything cleaned up easily. The seller could have sold these for big money if he took the time to clean them up.
Before:
After: