The fuel draining back after a failed start is normal.
How is the distributor? Any side play in the shaft? If there is, the points will not stay set. They can do strange things, the gap may look good, then change when running. Points are always a source of problems, the new ignition parts are not good quality.
You say it has a 6v coil, did you mean a 12v coil? Be sure it does have the correct coil, or coil/resistor combination. Some coils marked as 12v still require a resistor. If you have an ohm meter, the correct resistance across the coil primary terminals, out of circuit, should be around 3 ohms. The wrong coil will cause short point life or weak spark.
Have you tried a test run with the air cleaner disconnected? There is a wire mesh element inside the canister that needs cleaning, it is often overlooked. It could also be clogged with mud dobbers or mouse nests.
A simple test of the engine integrity is to disconnect and ground the coil wire, open the throttle, hold your hand tightly over the carb, have an assistant crank the engine through. You should get a strong, steady vacuum, and your hand wet with gas.
If pulsing vacuum, very little vacuum, there is a serious vacuum leak, or a valve problem.
A quick compression test, pull the coil wire, open the throttle, listen as you crank the engine through. You should hear each cylinder load the starter equally as it spins through. An irregular sound, a cylinder that spins through with less resistance is an indication of low compression. If suspect, follow through with a real compression test.
Have the valves been set lately? If low compression shows up, take a look at the valve train, look for bent pushrods, broken valve springs, stuck valve, check the valve lash.
Hope this helps, I prefer cash over Paypal! LOL