critique this Magnum hop up, swap.

I have a plan for putting a 5.9 Magnum motor in my 65 Dart behind a 904 and 3.55 geared rear end. I am looking for any suggestions for making cheap power beyond what I have already planned for. Here is the plan.
I have a used Comp hydraulic roller cam with .480 lift, and 279 duration on both intake and exhaust, with 224 degrees duration @.050 on a 106 Lobe separation. If it will clear, I want to advance it as far as 102 to help it work with the stock 318 converter. It will have long tube headers, 1 5/8 tubes with three inch collectors going into 2 1/2 inch pipes and super turbo mufflers under the trunk area. (The spare tire well has been replaced with a flat sheet of steel.) Induction will be a dual plane air gap intake and 3310 Holley 750. Since I have to change out the valve springs, and want to look inside the motor a bit, a little back yard bowl porting is an option, along with a thinner head gasket if the motor will tolerate the extra compression? I could also back cut the valves if it is worth doing. Any other tricks or tips welcome.