Bit of a novice myself but you might find that 1605 would be a better choice for the Z axis, no doubt one of the experts will give you some sound advice before you reach the stage of ordering anything.
As for the pulleys have a search on the forum as it's been talked about a lot. Just make sure when you do your design you are going to have somewhere to run the belts, the X axis one in particular because this is quite a wide machine so you are looking at a belt a bit over 2.5 mtrs in length.