Safe 8 3/4 axle lift
I have 4 original A Body 8 3/4 housings.
All 4 needed straightening.
You can lift your car by the center and unless you have measured it before the first lift and now and the housing is still the same then you have no idea if you have bent anything.
This image illustrates things
Not to mention how does a housing get straightened
You apply force in one direction and resist it in the other.
If it was a cast iron center, and heavy wall tubes I would lift from the center without reservation.
But a formed sheet metal housing does not have the same type of strength.