Messed up firing order? I need help!

[PKRWUD]

Those are the correct firing orders. It has to be one of them. The backfiring, if through the intake, is probably due to a blown power valve in the carb. If the engine has an HO cam in it, then you need the 1-3-7-2-6-5-4-8 firing order. If it was built to stock specs, with a non-HO cam, than it has the 1-5-4-2-6-3-7-8 firing order. Make sure that the spark plug wires are completely seperated from each other, from the distributor cap all the way to the spark plugs. Then, set the engine to TDC on the compression stroke, and make sure the rotor is pointing to the #1 wire. This should enable it to start. With the vacuum advance disconnected and plugged, start the engine and adjust the timing to 10 degrees BTDC. Next, set the idle speed, and adjust the idle mixture. If the carb is good, this should work fine.

BTW, the easiest way to verify the piston is at TDC on the compression stroke is to remove the spark plug, and stick a wadded up piece of paper towel into the spark plug hole. Rotate the engine by hand until the towel pops out, and then go to the TDC mark (should be close).

Take care,
-Chris