Look on top of one of the center air tunnels of the intake manifold (I don't remember which side, so you'll have to check both. start with the drivers side). The firing order is usually raised numbers cast in the top of the manifold.
the firing order is 165432
165432 is the firing order for the 4.3 L engine
1.6.5.4.3.2
fireing order for 1997 astro van v6
Most Chevy v8's are 18436572.
165432 #1 cylinder is left front
Here is a link to Auto zone. Hope this helps you.
1, 6, 5, 4, 3, 2.
1, 6, 5, 4, 3, 2.
4.3 Engine 1-6-5-4-3-2
I think it is the same as the 1988 one that was previously answered. 1.6.5.4.3.2
the firing order is 1-6-5-4-3-2 1-3-5 driver side 2-4-6 pass side