One thing to note about shackles being used with snatch blocks (since you need one to connect to a tree saver); make sure you purchase a shackle that is rated for at least double the pulling power of the winch, since the snatch block doubles your pulling power. It seems that a lot of the kits out there do not account for this. Most 3/4" shackles are rated at 6-1/2 tons (13k), but an 8k winch with the line payed out to the first layer is capable of a full 8k, so double that is 16k (8 tons), exceeding the rating of the shackle in between the snatch block and the tree saver (which are probably both rated well more than that). I keep a 1" (10 ton) shackle with me for use with my snatch block.
As for purchasing the parts, I would order off of Amazon and pick and choose the best bang for the buck.