As I'm sure your aware trouble shooting needs to be a systematic process but often times it's easy to get side tracked and loose sight of that fact. At this point it might be a good idea to go back and start at the beginning. If you were to bring the car into my shop and explained the situation as you have here these are the steps I would go through:

1. Verify that your getting fuel. Pull the aircleaner and move the throttle, if I get an accelerator pump shot it's good, if not crank the engine and try again. If I still don't get fuel check the fuel filter, fuel pump and fuel lines until I've eliminated the problem.

2. Check for spark. Pull a plug wire and crank the engine if I get spark move to the next step if not, pull the coil wire from the dist cap and try again if I get spark there the problem is in the cap or rotor. If still no spark check the point gap and insure the distributor is turning. If they are OK start checking for voltage in order at the points, coil, voltage resistor, firewall plug and switch. At this point you should have spark.

3. As the distributor has been removed to replace the manifold and there is a question on the balancer the next step is to verify timing and firing order. Pull #1 plug and bring #1 cylinder to TDC on compression stroke. (On the FE you can verify the timing mark by using a wooden dowel put in through the spark plug hole. Turn the engine over BY HAND until the dowel is at the highest point at which point the cylinder is at TDC and the timing marks should line up at zero. If they do not make a chalk mark on the balancer so you know where your at. At this point verify the location of the dist and the firing order. Once that is done. turn the dist until the points just start to open on #1 cylinder.

4. At this point the engine should fire, if not the next step I do is pull the plugs. If sparkplugs have been badly gas fouled THEY WILL NOT FIRE. In most cases they cannot be cleaned and dried enough to make them work.

5. If it still will not run The next step is to pull the carb and verify that I don't have a vacuum leak at the carb base gasket. Finally if the engine will still not run I would pull the intake manifold and see if the manifold gaskets slipped when it was installed (very easy to do when installing a cast iron intake in car). I would then install new gaskets REGARDLESS of what the old ones look like. I personally eliminate the use of the rubber end seal and run a bead of silicone in place of them. Also when I R&R an iron FE intake especially in car, I use my engine hoist. Besides saving my back it's easier to set the manifold in place without the gaskets slipping. If I didn't have the hoist I would rent one!!!

Hope this helps.