I did a shackle reverse on mine when I did the SOA. Didn't notice a thing. You will notice a slight improvement in handling if you're running springs with a lot of arch to them, like sprung under and 4" of lift. There are a couple of definate downsides to the shackle reverse however. Assuming you're gonna wheel this thing, the front of the frame rails where the new hangers attached will begin to crack. I've never seen one yet that didn't crack. Some minor work on the rails will cure this problem. The front axle will move backwards durring compression or hard braking, so a longer slip yoke will be needed on your front drive shaft. Also, the front tires will move back more, hitting the inner fender wells. One other minor thing, when you jab on the brakes on the hiway, the front end will dive so far, you'll swear your front bumber is dragging on the street.
All things considered, I'd never do one again. They just plain aint worth the work.. Of course, this is just my oppion, and I've been known to be full of SH*T!