For performance upgrades, enthusiasts often "prepare" old mounts by filling them with liquid polyurethane to stiffen them.
Review: Fabrication Part 2 (e.g. a Motor Mount) - CS-STEM Network
: Transfer the template to your metal stock. Drill the bolt holes first to ensure alignment before cutting the outer shape with a cutoff wheel or saw.
If you are simply replacing a factory mount, "preparing the piece" involves readying the workspace and the new part.