Use a utility knife and straightedge to do the lay-out work as required, then re-scribe along those lines several times, depending on the thickness of the material. Flex the sheet along the lines and it will quickly fatigue and the individual pieces break free. Use a file to touch-up the edges as necessary.
These photos show a similar process for making moulds in which to cast lead car weights:
Because the moulds don't need to be too precise, it's not necessary to file the edges, but for a visible detail part like this, a pass or two with a file will improve the appearance and remove any overly-sharp edges.
If you're going to decal the car and the nameplates, a prior coating of clear gloss will improve the adhesion and the appearance of the decals.
The aluminum shown is .017" thick and very easy with which to work - the few passes needed with the knife will have little effect on the blade.
Wayne
