Okay, the vibration was stopped. New motor mounts in place, it was time to tackle the exhaust header. The 4.0L engine is prone to exhaust header issues. And, the exhaust is a critical part of an engine. You can improve performance of an engine by increasing air flow through the engine. Basically, the hot exhaust gases need to go somewhere. Why not through clean bends of an aftermarket performance header?
The stock 4.0L exhaust manifold would not place well in an airflow test. On the other hand, aftermarket headers are tubular and designed for efficient air flow.
Take your pick. There are several vendors providing quality products in a variety of price ranges. Each has their advocates. Some advocate for ceramic coating. All agree on tubular construction.