If you're sticking to the stock exhaust manifolds, the GT40P will work fine even with the different plug angle. You will need to some grinding, mostly on #8 but nothing really hard or bad. On 5,6&7 just some really minor grinding, mostly just removing casting flash at the seam. The stock cam will work pretty well. I wouldn't go more then the Mustang 5.0 cam unless you change the valve springs. Just leave the stock cam in and you'll be fine
You need the 289 style oil pick up. Buy a new one, they're cheap enough.
I'm not a complete idiot, pieces are missing.