tail lights leaking water into trunk

I found this car that I would like to get but has some water damage in the trunk. It appears to be leaking from the tail lights since I cant find any other place that it could be summing from. I found a fix for it with that sticky black stuff but this issue was left to fester for years (it seems) and the spare tire area is all rusted up. The spare is useless which is fine but the part that it screws onto has rusted off. I think there is a rubber plug in the center of the area....at least that what it felt like. is this an area that can easily be repaired? I didn't notice exactly where the fuel tank was but it seemed to have been more forward...if im not mistaken.

Is there another place that I may have over looked where the water could possibly be coming from? everything else looks perfect so I think the tail lights are the culprit. And since they appear to be aftermarket red/clear tail lights I just assume the guy didn't seal them off.

Stock 2001 tail lights are not red/clear...right?

Thanks in advance.