Norbie is correct but before you jump the gun check what year your Z20 is. If you have a later one it will have round engine mounting rubbers, where the early has square rubbers.
If you have round, then the engine and gearbox crossmembers will be the same as the JZA70 meaning all you require are the engine brackets from the JZA70. Since you already have the engine, if all you need is the brackets then dig some up. If you have the early crossmember and mounts, go buy a halfcut.