bucket seat mounting location.

Ok, so I just bought my first Mopar. 69 dart, I came with the bucket seats, only the drivers side was bolted in. There were pretty existing holes for the passenger seat( not factory, drilled by someone) this is an original bench seat car, it has brackets built into the floorpan for the bench seat. The buckets are complete seats with seat frames( adjuster mechanism) and studs sticking down. I lined up the pass seat with the holes and mounted it. Besides not being evenly spaced from the center, the seats seem a little low. My question is, are the floor pans different from bench to bucket, are there brackets missing? Are there adapters I can buy?
Thanks in advance guys!!