Engine core pack type of vauxhall vectra 1999 t reg?

You need to be more specific. Is it the coil pack you refer to or the ECU? Also thty didn't make a Vectra 1.0 so either model (i.e Vectra or Corsa) is wrong or engine size is. If you get another engine you need to get the ECU and the ignition at the very least from the other car and ideally the whole lock set to as your key won't work. You can get the replacement ECU and keys re-coded I believe. If you get the head skimmed you'll know it's ok and you know what the engine is like now anyhow. Buy a second hand engine and it will probably cost you more plus it could be rubbish so costs you a lot to have it fitted and then if it's duff you'll have to pay out again.