Step 2: Measure
Once you have your seat removed, you can take some measurements to establish the 2 bolt patterns that you are trying to adapt. The car will have (most likely) a simple 4 bolt pattern, and the seat will have (most likely) a different 4 bolt pattern. The goal is to make a bracket that contains both bolt patterns.
Once you have the measurements, it helps to overlay them on top of each other to visualize how the two will fit together. I used Autodesk's AutoCAD Mechanical 2012 for this step, as it is readily available on computers at the TechShop.