for everybody that is using offset shackles

Ok, thanks. I kinda like @famous bob idea.

It's more work that way, but it would let you maintain the factory angle on the perch. The first time I did it I kind of used that method, I cut the stock perches back and used the remainders to set the angle on the new perches, then removed the leftover bit of original perch. So at the end it was just the new perches on the axle, not an extra wide perch.

I've found that even though it would seem like more work to pull the entire rear axle, it's actually easier to just pull the thing, set it on a bench, and weld the new perches on at the right angle. Because unless you run the factory ride height, the factory perch angle may not be right for you anyway.