Not sure about the slots in the bumper, but this is a '71 and up bumper...
Bumper in question
Brake lights are definitely '70. And they're '70 Only. '71-'73 looks like the top picture. Maybe just a repro bumper with incorrect slots?
Either way, I don't see it getting more than $14k. Its a nice car, but it certainly doesn't sound "all original" if its had a repaint and quarter work. And its just a 318/auto on the column with a bench seat and non-power drums. Maybe if it were a 340 car, or a 4 speed, or had buckets and a console etc. it might go for more.