Here goes my .02 cents, take it of leave it:
347 is the total wrong approach to try and make that kind of horse power. Look at doing a 363, 4.125 bore will unshroud the valves and make considerably more power than a standard 4" bore. What crank, rods and pistons are you going to use? How much compression? Hyd. roller or solid roller cam? These have a lot to do with deciding on the heads. Do you want to make 1000 fly wheel hp or rwhp because that is a world of difference. Make decisions like this before you even think about deciding on intake manifold and throttle body sizes. Injectors and fuel system components can be a thought after all of this. Are you considering a stand alone fuel injection system? Twin disk clutch at this power level I'm assuming? Is the TKO even going to live behind that much hp? What type of chassis work will you be doing? bolt in parts at this HP level don't exactly jive, sure
control arms and stuff will bolt up but what are you doing about torque boxes? Cage? Subframe connectors, and I'm talking about legit through the floor type connectors, not some weld to the bottom of you floor and think it's good type deal. The rear, you don't need a 9" or the hassle associated with making it work with your stock
suspension (been there done that) after all that time and effort, you want to make 8 second hp and only go 10.0's?
Personally before you go jumping into this 40,000$ mess plan this out to the T carefully and don't just start throwing your money around. This is a big undertaking, bigger than most people realize. Ask me how I know...