My first build, I need some help please

First question: What is the emphasis on street versus strip, if you had to choose one or the other? And are the strip times listed a real objective or just an idea on what might be good? I ask because strip can fight street manners.....and that is all a bit subjective anyway!

I'd suggest going for 450 HP since this is your first build and if it is going into a 2900 lb car it WILL be plenty fast. Besides, the conventional wisdom is the stock crank is good for up somewhere in that range. If you focus on that 450 number, things will come together pretty easily.

For your pump gas requirement, you need to learn about static and dynamic compression ratio. Again, conventional (safe) wisdom is to limit SCR to 10:1 for AL heads and 9.5:1 for iron heads. (Higher SCR's generally go with wilder cams and more aggressive engines.) This will put you where using flat top pistons is a good choice. And you don't want to go too low on CR or the low RPM torque will drop and it will be doggie on the street. (You won't be able to change the torque converter stall speed like in an auto trans to compensate.)

As for milling, milling the heads is for setting the combustion chamber size to get to the desired CR. Milling the block will be good for getting the deck squared up to the bores, and to fit the pistons so that the tops come up near to the top of the deck (zero-decking). It also effects the CR. You would be well served to learn how to use a compression ratio calculator tool (available online) for both static and dynamic compression ratios.

BTW you will need a good clutch, and I'd go with an HEI ignition system, not the MSD.