What is the cylinder numbering of a 1964 429 Cadillac?

The 1964 Cadillac 429 (actually 429 cubic inches, not 427 as sometimes mistakenly stated) engine used a 1-5-3-6-2-4 firing order. This is the order the cylinders fire, not a physical cylinder numbering. There's no standard "cylinder numbering" system printed on the engine itself in the way modern engines might be. The firing order is the important specification for ignition and other aspects of engine function.