What are the cylinder numbers on a 4.3L GM engine?

The firing order is what's important, not the cylinder numbers themselves as that can vary depending on the specific application and year. However, the 4.3L GM V6 engine typically uses a firing order of 1-8-4-3-6-5-7-2. The cylinder numbering itself generally follows a pattern going from the front of the engine to the back, alternating banks. But consulting a repair manual or diagram specific to your exact engine and year will provide you with the most accurate cylinder numbering.