Are you saying that Adam and Eve's flesh changed after they ate?
The Scripture talks about man's flesh as being sinful. If Adam's flesh was not sinful flesh before he ate then his flesh went from being not sinful to sinful. That means his flesh changed. However, the Scripture never teaches anything like that. In fact. Paul says, with reference to Adam, that there is "one kind of flesh of man".
What the Scripture does say as the result of their eating, is that their eyes were opened to know good and evil. They now knew what they had done was evil (wrong) and that the gods (angels) were good (right).
If Eve's flesh was not sinful then she would not have desired something that was sinful. But the fact is, she did desire something sinful. That shows that her flesh was sinful flesh.
The wages of sin is death and death is the last enemy to be destroyed. Therefore, when death is destroyed, so is sin destroyed. And since sin begins in the lust of the flesh, the flesh must need to be changed in order for death to be destroyed. That's why Paul teaches that we must be changed and made immortal spiritual bodies so that death can be conquered. The spiritual, immortal body, therefore has no lust which would lead to sin and therefore cause death.
I am saying there was no sin in Adam and Eves flesh prior to when they ate the fruit.
Well, yes, Adam's flesh changed. Before, it was perfect. After eating the fruit it was sinful. Your use of (1 Cor. 15:39) doesn't work. It is not used to contrast sinful and perfect flesh. It is used to show the distinction between the flesh of man, animals, fish, and birds.
There was nothing sinful in recognizing that the tree was good for food, and that it was pleasant to the eyes. That was all true. Her desire to have it to make one wise is due to the deception of satan. (Gen. 3:4-5) "...Ye shall not surely die:...your eyes shall be opened, and ye shall be as gods, knowing good and evil." And God was very clear that it would be the act of eating the fruit that bore the sin in man. (Gen. 2:17)
The fruit itself was not sinful. Eve could desire it all day long, but that was not sinful. She probably desired the fruit of the other trees also. No sin there.
Yes the wages of sin is death. That shows Adam and Eve had no sin until they ate.
The 'spiritual body' you speak of will still be a body of flesh and bone. (Luke 24:39)
Good-Ole-Rebel.