Yes I build half my turbo kit from ATP (oil feed/return,coolant, every tiny fitting, nut and bolt and even couplers.)
You can get everything you need there(3bolt adapter, 2 bolt adapter, t25 gasket, 5 bolt gasket, t25 drain gasket, 9 nuts for the studs, 2/3 Allen key bolts for the adapters respectively.)
While your there I'd suggest a new ATP wastegate as you have to modify the wastegate bracket(keep from your old turbo) and re-clock the turbo
The exhaust manifold gasket and s to j pipe you will need to get at the dealer.
The 2 bolt adapter is for the compressor inlet(2.5") and the 3bolt adapter is for the compressor outlet(2"). If I recall the bolt sides for those is m8 for the 2 bolt and m6 for the 3 bolt. Also the 3 bolt adapter comes with a vacuum fitting. Use that as your vacuum source for the wastegate as it gives a better reading compared to stock location.
I almost forgot that the s pipe needs to be modified. The 5 holes line up 98% perfect but 2 of the holes need to be enlarged. You can get a machine shop to drill out the cast iron stocker or you can pick up an aftermarket and dremel it out