Alright. As Adam has said, it's pretty easy having the donor car and it's mostly a case of stripping the SRi and refitting it to the Combo. The engine and gearbox should bolt straight in. The Z16SE will have a Getrag F13 gearbox, where the SRi has a F17 box. Use the SRi box as it'll be stronger than the F13 anyway. Depending on the mileage on the SRi, I'd also take the opportunity to replace the clutch whilst it's out. That will be around $420 for the kit from Australian Clutch Services in Wingfield. Exhaust may need some modifying, but that shouldn't be too hard. Driveshafts should be all compatible between models. Also, if you don't know the service history on the SRi, other thing is to fit a new timing belt kit and water pump.

Apart from the physical fitting of the engine, you need to use the ECU, injection loom (the engine's own wiring loom), key chips and transponder ring module from the SRi. As well as this, you need to remove the engine bay loom from the SRi and place it in the Combo. This loom pretty much goes all over the engine bay, including the fusebox and to the body control module (BCM) case, where the loom enters the car. It's not all that hard to swap the looms over (I just did it recently in my SRi, as I needed a different loom for the Z20LET engine). I'd probably swap the BCM module over too, along with the dash cluster. The only thing I can see that might be an issue, is the ABS. SRi has it, Combo doesn't. I wouldn't bother swapping it over, but I believe I can switch it off in the ECU using an OP-COM scan tool, seeing as you're also in Adelaide (I'm out in the Northern Suburbs, where teeth and shoes are optional).

There was another user on here, goes by the username @Chris R (not to be confused with myself, I didn't even know the guy existed when I signed up), he did the same with his Combo, I know he was working on getting the cruise control working and what not, but if that's not an issue, I think everything else should be reasonably straightforward.

Where I used to work, we had two Z14XEP (DOHC "Twinport" 1.4L) equipped XC Combo vans. Indeed, they were pretty gutless and I think they should've been a 1.8 straight out of the box. I actually have a SB Combo with a SOHC C14SE engine at the moment, but the C14SE is seized up and hence, this beast will copping the Z18XE I pulled from my SRi. Sure, the SRi in standard form is pretty zippy, it just didn't have enough killawasps for my liking, so I've put a Z20LET Astra Turbo engine in it instead.

The biggest problem with the Z16SE is the fact that here in Australia, they only ever came out in the early XC Combo vans. No other vehicle sold by Holden here was fitted with that turd of an engine. Unless your name is @adam_92 and you have an imported Vauxhall Astravan.