It's always best to set certain goals, based on the application of the engine (car, truck, stock, race, torque, econo...). If you would define what you want to do with the engine, and what body it will be in, it will make any estimates, recommendations, etc. much easier.
FWIW, Edelbrock cams are generally "generi-grinds" available through several brands names, all coming from the same source. Depending on what you want to "do", there may be much better grinds available through cam grinders like Comp, Crower, Lunati, etc.
Long-tube headers ALWAYS make more power than "good" manifolds or shorty headers, provided they're a decent brand. If maximum power is the main goal, "ease of installation" should be a secondary concern when buying headers. Degree of difficulty varies with body and size of the headers.
The 600 will be out of "breath" before the heads are. Good pump-gas head, though, 441.