crazy tarzan
+1y
pinion angle is affected by the change in orientation of the rear drive shaft vs the differential and transmission. 3" should be ok, on jeeps (90's and up at least) up to about 3" of lift is ok, beyond that it begins to cause vibrations in the driveline, and transfer case drops of about an inch or two are required unless you tilt the differential up to compensate.
That said dropping could be considered lifting in reverse. If your driveshaft is more towards level you shouldn't have any problems--remember they were engineered to have some drop in the bed and still work for hauling loads.
It should also not matter if you drop the front the same as the back--they are not connected (unless your dropping a 4x4), hence the front won't affect the drive shaft angle, and you would never be able to achieve the 'raked' look other wise.
And I've seen numerous mini trucks that apparently it was really easy to drop the back (or break as may be), not so much the front. Always wondered if the felt 'lighter' going down the highway like that. . .