The 2000 Chevy Astro van with the 4.3L Vortec V6 engine uses a distributor,
not individual coil packs. Therefore, there's no "coil firing order" in the same way as engines with individual coil-on-plug systems.
The firing order for the 4.3L Vortec V6 is 1-8-4-3-6-5-7-2. The distributor's rotation and internal components manage the firing sequence based on this order.