My first build, I need some help please

Facts:

1) I have a 340 block that had to be bored 0.030 over stock (that was the least I could, one of the Pistons had rusted in there horribly).

2) I'm going to run a stock crank.

3) I have a set of X heads that I haven't built yet, but I'm looking to build them to the nine's.

4) I'm currently eying the MP Purple Stick camshaft, Hydraulic Flat Tappet, Advertised Duration 284/284, Lift .484/.484. It's the biggest Purple Stick that's hydraulic. Should I go with one of those mechanical ones instead? They have longer durations and higher lift range, but I don't want to have to take the motor down and adjust the valves like I have heard you need to do with mechanical cams, please help me there.

My main question is what kind of pistons will suit my build the best? I'm going to go with a forged set for sure, but do I get Flat Tops, Dishes, or Domes? Here's the one's I am currently looking at (everything is open to suggestions):

Flat Tops - http://www.summitracing.com/parts/ros-99625/overview/make/plymouth.

Dome Tops - http://www.summitracing.com/parts/ros-99626/overview/make/plymouth

What does anyone here suggest? Also a rod selection would help, I don't know a lot about them specifically.

In any case will milling the heads down be a good idea? I'm wanting to max out my motor's potential. My only restriction is I don't want the compression to be too high for pump gas, the highest I can get is 93 I believe (I can double check that tomorrow). I know that depends on my piston choice and scam combo too because I obviously don't want to run the valves into them.

My goal here is 450(at least)-550 horsepower(if I could). Car will be ~2900 pounds. I'm planning on running 3.91's (in an 8 3/4). I'm using an A-833 OD with the GearVendors unit behind it (transmission ratios like so: 1st 3.09; 1st over 2.40; 2nd 1.67; 2nd over 1.30; 3rd 1.00; 3rd over 0.78; 4th 0.73; 4th over 0.57). If it was a 10 second car that would be awesome, but shooting for at least 12's. On top of the motor I'm running a Six-Barrel. The heads and intake will all be port matched. I have headers as well, I'll need to check what size there, but I'm pretty sure they dump at 3". I'm going to do electric water pump, fan, and fuel pump. Manual steering set-up, so I ought to just have one belt, to run the alternator. I'm probably going to pick the MSD electronic ignition kit, Digital 6AL, distributor, wires, & coil (unless there's something better). Really price is no object, I'm looking to build what I'm referring to as Street Stock. It'll appear pretty tame, but not be a full on strip-only race car.

Thank you everyone who read the entire thing. I know it was pretty lengthy, but I see a lot of people post with only snippets of information and I really want as much advice as possible. I did use the search function and found a bit of relevant information, but thought it would be best to lay down a fresh thread so I could cover everything at once (I hope).

Cam link: http://www.summitracing.com/parts/dcc-4120231ac/overview/make/plymouth

Ignition link: http://www.amazon.com/dp/B00W6DL1D4/?tag=fabo03-20