Justin,
If you are not dead set on a 4 bar rear suspension, we have a new torque arm suspension that requires ZERO fabrication or welding. Since you are going to upgrade the rear end as well, our kit developed for the Ford 9" rear end already comes with one for $3k. This particular kit is designed around a HD Strange housing complete with 3.25" axle tubes and back brace. We can build the rear narrowed too so you can get that offset you are looking for with 4-5" lips on the wheels. Additionally we can install any housing end on the rear to accept whatever brakes you want to run.
If your interested, just check out some pics
HERE on the website and feel free to ask any questions!