I have installed a 3in spring lift (Front) and 3in spring add-a-leaf (Rear) on my 79 4x4 short bed. It appears the rear shackles may be to short since the angle of spring to frame mount is reversed (compresses toward the front instead of the rear). I have not set the vehicle on wheels yet. Axle attahced to the frame are still suspended from the ground. Is it necessary to increase the shackle length? Do I need longer rear shackles? Are there others in this forum who have similar experiences? ... Thanks

maybe
but shouldn't be necessary
plus
you can't tell much if the weight is not on the wheels
which i can't tell exactly from yor post