This is just a curiosity type question. In 19dart74's previous post, it shows he has a 318 engine. In post#10 72bluNblu states that all the V8's 73+ were disk/drum and therefore BBP.
So does this mean his car originally came with a slant 6.
These cars are like 50 years old so a lot can happen. Someone that ordered the car talked the dealership into taking the disks off, some drag racer thought they needed drums for less rolling resistance, somebody was parting this car and stole the disk set up for another car. Or yeah, it was a slant 6 car that’s had a V8 swapped in at some point. Also a good reason to check and see if the bolt pattern on the rear axles is 5x4” before ordering parts for the rear.