You will likely need injectors to get your goal, I don't personally run a set of twins on mine. I run a s475 single. I have friends that run s472 all day while towing without issue. the s472-75 can make over 800 HP with no issues. the head studs are a good idea ,but im still on my stock head bolts so far with custom tuning. MCC is built into your Mini max ,you can pull the stock tune out and look at it without having to pay H&S for the unlock code ,but when you go to install the custom tune on the truck its 200 dollars last I checked plus the cost of your custom tune from your tuner.
On the trans it all depends I run a torque shield and GJ lite transmission fluid and all as been well. I believe with custom tuning you wouldn't need the torque shield up to 650 HP. It is good for peace of mind though