welcome to the garage! you've found the best "interchange manual"
someone here who has a pre-40 truck will know if the difference is as drastic as the later years, but while the 39 and 40 fenders should be the same, the 1/2T and 1.5T are different due to the difference in wheel sizes, the opening being a different shape ... will bolt up, but usually look kinda goofy ... check the gallery and compare the look of light and big trucks
Bill
