the header installation thread.. well, ??? anyway...

More than 4 inches, I lowered a Dakota that had a 4x4 axle on a 2wd truck. It lowered the rear bumper a good 12 inches. Just get a new set of springs. You can run cast iron manifolds and a good dual exhaust with nearly the same street performance and they dont leak. Headers are notorius for being thin and rusting out,leaking,hard to install,burn plug wires, and rattle.