Let's say the 489 makes 530ftlbs. Let's also say it makes 530ftlbs from 3000-5000rpm.
530ftlbs@5000rpm=505hp
530ftlbs@3000rpm=302hp
If you want an engine to make HP during launch, it needs to spin some rpm. With radials the tires also need to dead hook. With hooked radials, a car needs some time to gain ground speed before clutch lock-up, otherwise the engine gets pulled down where it doesn't make much power.
Say you want to keep engine rpm above 3000 with radials during launch?
...With 3.23 gears and 28" radials, the clutch is going to need to slip to about 28mph.
...If you want the engine to stay above 4000, the clutch is going to have to slip to around 36mph.
Swapping to a more appropriate rear gear would reduce the need for clutch slip time.
You might think that if the engine makes the same torque at 3000rpm as it does at 5000rpm, 60's would be the same. That's not the case, as an engine's rotating assy absorbs torque as it gains rpm. The less rpm an engine has to gain on it's way to the 60', the less torque it's rotating assy will absorb. Less torque absorbed by the rotating assy means more power will be available to accelerate the car.
If you want to play with how long the clutch slips vs how far the clutch pulls the engine down during launch, you do that by adjusting clutch clamp pressure. Dialing in launch clamp pressure helps cure spin/bog problems, also reduces the tendency to wheelhop.
A clutch hit control device such as my ClutchTamer makes adjusting clutch clamp pressure during launch much easier, without compromising the clutch's overall ability to hold torque. I often hear the 'tamer also makes bracket racing with a stick fun again
Grant