Shackle relocation

Wanting to relocate my shackles further back. I have a bumper fabbed that ties into the stock bumper mounts and the stock hitch mounts. I can't remember exactly but I think the angle iron that acts as the nutserts goes back like 15"+ into the framerails. Is this sufficient for suspension? I've searched and can't find any exact info.

Just get a set of these and call it done.

http://naxja.org/forum/showthread.php?t=956630

That's a great idea, not too hard to make either. Thanks