On a factory 8.75 A body rear, the perches set pinion at up 5*.
When installing them myself, I never use the factory setting. I usually weld them on anywhere from 0 to 2* up depending on application.
On a street driver, you usually don't want more than 3* down compared to tailshaft when installed in the car. Driveshaft has nothing to do with it the way I go about it.
