first of all, the z18xe1 came in late vectras and will have an immob. The reason you want one is its an 1800 smallblock, not the orginal X18xe big block.

The spi engine you have wont be the same as the c16se, it will have a shit cylinder head.

Anything without an immob you need 9 wires. Anything with one, you need to make sure you get the transponder from round the ignition barrel and the chip in the key from the donor car.