454 ci gm turns over hard backfires timing ok acts flooded

have you checked the cylinder compressions as backfire and blue smoke can be a symptom of low compression , either rings or valve seats but would need a dropdown test to be sure

Being that there are misfire codes, (300 series P codes), and it's flooding I would put a fuel pressure gauge on it and try to check the injectors and the fuel pressure regulator for leakage. If the vehicle has sat for a while, 1 or more of the injectors may have stuck open. If the fuel pressure is way to high it can cause the pressure regulator to leak. See if that helps.

Have a test done on the glo-plug system as it appears that they have burnt out and are not pre-heating the cylinders or providing a source of ignition for the atomised fuel from the injectors

What engine ? 4.3 , 4.8 , 5.3 or 6.0 l What fuel injection system ? What is the fuel pressure ? Do you know what fuel trims are ? The fuel pressure regulator's are prone to leaking to leaking on thses SPI injection system./
How to identify and repair leaking fuel pressure regulator GM CPI system...

fuel pump or map sensor

do u mean hard to turn over or fire engine

When it's very cold and the car will start right away, the most common thing that happens is the engine will flood. When you turn the key to start, the gas is sprayed into the engine. It does not know that the car didn't start and will continue to spray gas as long as the key it turned to start. That is why you should not crank for longer than 20-30 seconds at a time.
Then if it will not start, hold your gas pedal all the way to the floor, and the gas spray is stopped, so that the extra gas can be expelled. You can now try to start agian normally.

This problem can be several things. When your engine is cold, your computer is in a "closed loop" and just pretty much keeps the engine running until warmed up. After reaching operation temperature, the computer starts reading all the sensors. If one sensor is not connected or is defective, you will experience performance problems. Most of the time this will turn on the check engine light, but not always. Second is the fuel pump. This too will cause erratic engine problems.

try this,, pump the gas a few times and take your foot of the gas then turn the key over and see what that does.. let me know
good luck ray

are you getting a spark on your spark plug????/