Will a Stock 489 handle 700hp?

For what its worth, I run a 742 3rd member in my MO875 (8 3/4) housing with 35 spline axles and a spool, foot braking at the track in my 3250lbs car and it holds up fine (runs low 10's). I also drive it all over town with my 5000 rpm converter and 4.10 gears. If built right it works just fine.

.....BUT, if I were you (with the power that you think you might have), I would either go with a Dana, or a Ford 9 inch. I would probably lean toward the 9 inch because there is a better selection of gears.