Back in 96-98' I worked the tri-star show circuit and was around Muhammad for 2 years. It has his basic letter formation, but we do not know what his condition was at the time of signing but for the most part I don't think he signed this.
I'm not 100% certain but it seems to be a classic case of the book being signed by the author at a signing event and then someone forging Ali to try and claim he was at the signing also.