I agree...

Keep in mind that the piston comes to TDC twice before the spark plug fires. You need to confirm you're on the compression stroke before installing the distributor. It's the most common error and may or may not be your issue of course.

You can go old school and disconnect the coil wire, and pull the number one plug, put your thumb over the plug hole and turn the engine over (with the starter slowly) until your thumb is pushed off by air. That's the compression stroke. Then adjust the crank position to TDC on the balancer which should be very close and reinstall distributor.

When I'm building engines I keep track of which valves are open on the compression stroke at TDC, that way I can confirm I'm installing the distributor correctly with little hassle.