Bench to Buckets...need help!!!

Wow, I see what you're talking about now. The floor in your '75 is significantly different than the one on my '70. I wonder why the factory made such a radical change. I'll bet your brackets would work in an earlier a-body. Nevertheless, I would either return them and fab your own, or modify the ones they sent to work. I think you're going to want to keep the seats lower than higher - like maybe cut the inboard mounting tabs off and reposition them up and extend or space the outboard ones to level it out.