changeing yoke on 489 8 3/4

Like BJS said there is an adapter joint from 7260 to 7290, it is your best way to go.
Your 741 is most likely course spline while the 489 is probably fine spline. But even if the splines were the same you would have to change the crush sleeve on the 489. Plus to get the pinion bearing drag right the carrier needs to be removed from the housing so the pinion is spinning alone.
I am sure that there are plenty of people that will tell you that they have done it without removing the carrier with no proplems and this may be true but the correct way is to not have the carrier in the housing.

Here you go.
http://www.moparts.com/Tech/Archive/shaft/4.html

Chuck