what should i expect to pay 8 3/4 chunk?

The 742 doesn't use a crush sleeve it uses shims to set the pre-load. The 489 uses a crush sleeve but Randy's Ring and Pinion sells a solid spacer so you don't need the crush sleeve. Also the 489 uses a tapered shaft on the pinion gear......IIRC it tapers from 1 7/8" to 1 3/4" like the 742 rear.