8) codes are the last thing you want to pull. first check your fuel pressure, it should be between 32 and 45 lbs. if it is higher than that, then either the fuel pressure regulator is going bad, or you have a clogged return line. since oyu have already done the ignition, it is time to run some injector cleaner through the system, and NOT through the gas tank either. you have a pressurized bottle of fuel injector cleaner that hooks up to the shrader valve, and you open the can's valve untill you get 32-35 psi(you want the regulator to remain closed so you dont have cleaner going to the tank). you also disconnect the power to the fuel pump. start the engine and let it run out of cleaner. then reconnect everything and check you a/f ratios. at this point if you have done everything else, then start testing your map sensor, throttle position sensor, coolant temp sensor, air charge temp sensor, etc. to see if they are all with in range. if not replace them. one more thing is to have someone read the data stream from the computer while the engine is running as that will tell you exactly what the engine is doing at that moment. at this point you now pull your computer codes. just remember that just because the computer throws an O2 sensor code, that only means that is the circuit that is being affected, NOT that the O2 sensor is bad(it could be but there are a few tests that need to be run first. check the shop manual for those tests depending on what codes the computer throws out).
A Ford 300-6 with a one barrel Carter YF carb is pretty nice to work with 8) 
