A full scale Egyptian Pulley, limestone, with 12 inch diameter roller, was successfully tested duplicating a 5,000 pound weight lift (52 degree incline) and is shown in the below PHOTO.
The first four SKETCHES below show how the stone block on a wood sled could have been pulled up and unloaded at the top. The first sketch is a simplified cartoon showing the basic operation of the Egyptian Pulley (but does not illustrate loading/unloading the stone).
Sketches 2 and 3 illustrate a likely stone unloading technique in which a locking "key," holding the Pulley in (horizontal) position, is removed as the stone/sled reaches the top edge. The stone/sled is then simply pulled over the edge and the Pulley transitions horizontally (in the direction the rope is pulled).
Sketch 4 shows the use of a counterweight and two Egyptian Pulleys to lift the stones during the last stage of construction (with relatively little surface area on top).
Sketch 5 is an illustration showing a grooved "rope roll" (approximately 14 inches axial length) found at the Step (Djoser) Pyramid. The Step Pyramid predates the Great Pyramid by more than 100 years.