It's covered pretty well elsewhere, but difference between the K20A(2) and the K20Z is that the K20Z has type r cams and a different transmission. The transmission has a lower final drive (like the type r), but not the closer 4/5/6 like the type r. More importantly, the K20Z has a different speed sensor output and uses a different ECU. This does matter for a swap because the easiest way is to use the 02-04 K20A2 ECU rather than the 05 K20Z ECU, which currently cannot be re-programmed.
The mounts are the same. K20Z is rated at 210 hp vs K20A 220 ps and K20A2 200 hp. In practice the 10 hp difference between the K20A2 and K20Z is less than the normal variation between engines, so don't get the K20Z solely for the extra 10 hp.
To remove AC & PS get the Civic Si idler pulley (~$100 from dealer, parts number should be on this forum if you search) and use a 7 rib 50.5 inch belt (pep boys 7K505 or something similar).