rear shackle relocation

I just started research on moving my leaf springs inward on my 68 barracuda and I see a couple people said to use the existing hole in the frame to relocate the rear shackles. this hole is forward and was wondering if that would cause any problems. also the car is completely stripped down no motor trans nothin i took a reading on my pinion off the yoke where the ujoint clamps bolt with a digital inclimeter and it read 5 degrees up with the tires on the ground, is this an accurate reading to set my new rear end at? Is this a factory setting I always thought the pinion should be pointing down 5 degrees.

Thanks any info would be appreciated