#1 is the front cylinder. #6 is the rear, and #1 and #6 have the piston at the top of the stroke at the same time. When #1 is on the compression stroke both valves are closed, and there's no good way to know when the piston is exactly at the top. However, when #6 is on top, the exhaust valve is in the process of closing, and the intake is opening. Get the #6 cylinder "rocking", (both valves moving in opposite directions) and #1 (the front one) is ready to fire. Get #6 rocking, and time the distributor so the rotor is pointing toward the wire going to the front cylinder.
If it backfires through the carburetor, yes, you've got fuel and fire, but it's firing when the intake valve is open. Once you get the distributor rotor pointed to the #1 plug wire, the rest of the wires need to follow in the proper firing order in a clockwise direction around the cap. The firing order is 1-5-3-6-2-4. It doesn't matter which wire you use as #1, as long as that plug gets fired at the proper time, and the rest of the cylinders follow in order.
Jerry
