[ford38v8]

From yout pictures, it appears that the key is extending outward, thereby raising that end above the flat bed of the keyway. Apparently, all keys are not equal.


On another issue, I suggest that you remove the key, and with the use of grinding compound, install the drum and nut loosely, turning the drum by hand to seat the taper to the drum. This step has been made considerably more important now since you apparently have used emery paper, which provides no control of the depth of cut. Failing to perform this crucial operation will put your key and keyway in control of the drum remaining in position, rather than the taper to drum contact, which by design is intended to solidly seat the drum against turning on the axle.