Overheated the engine and now not starting

I would be starting with a compression test, report the readings here for further assistance.

You need a compression tester that screws into the spark plug threads, crank the engine over and it will give you a compression reading, just make sure that the leads are away from the tester as you don't want a spark jumping and giving you a boot. You may be able to hire a tester if you can't get one from a friend, make sure it is one with a flex hose as you don't have a lot of room to get in, also what model Commodore is it?

OK, comp test will tell us a lot about what is going on in the engine, if you get a comp that is very low compared to the others, squirt a small amount of engine oil into that cyl about a table spoon full and re test the comp, if it comes well up there will be a ring problem if not a gasket or valve problem will be causing the low compression.

https://www.2carpros.com/articles/how-to-test-engine-compression

Not good, 120 ok 3at 90 fair to poor 50 and with oil 65 will be valve problems or head gasket and 0 is a big worry try that one again and with some oil if nothing will probably be top end problems, but with the other poor readings, it will be a waste of time doing the heads as the bottom end is just about stuffed as well, may be time to look for a good second hand engine if you want to spend any money and keep the ute, trouble is a VS is worth not a lot these days and you have to weigh up the cost of re engine or scrap it, you will still be looking at 2-3k + to get a second hand engine fitted and do all the extras that will have to be done to ensure that nothing else goes wrong, may be worth getting a few quotes, where are you I may know some one you may be able to talk to first hand that you can trust.

Yeah those numbers are very bad. A normal engine will run about 135 psi and up and you want all of the cylinders within 10% of each other. So the range for yours, using the 120 cylinder as "good" you would want to see no lower than 108.

Hate to say it but I think you need a replacement engine or IF the block and heads test OK you might be able to rebuild that one. Overheating most modern engines is a killer, they don't have the amount of metal in them like the old engines, thinner castings and aluminum to save weight make them easy to hurt.

I will ask a few mate if they know anyone on the gold coast, I am down in Vic myself.

Ok good luck with fixing the car.