Would the plates make my b10 with A15 legal? Is this how they cross check which engine should be in my car or do they do it some other way?

No, it won't affect legality. But if the law in your state says "as long as you make a new plate, then it's legal"... nah, it is unlikely any state would pass a law like that.

If your goal is to fool the inspectors, Yes, it might work. That's called 'fraud'.

I'd take a CA18 one

when i went to register my ute here in VIC, becouse it had the same owner from 1982 till 2006 the details of the car (engine no*, trans, number of seats etc) had not been entered into the current system (changed in the late 80's), so all they had was the VIN and rego number and who it was last registed to. so when it came time, they had to take down all the details on the two plates to register it. so if i had of known i could of put in a a15 or some thing and no one would have had a clue (cep a datto fan)

Many inspectors don't have a clue. They might say nah these cars never had XX motor. BUt you can say, AH, but the very last of the deluxe's from 1972 had the larger engine for the JDM market, and this one got shipped down here. It's a very rare car mate! And many of them would be like Oh, really. Okay. Works really well with the police who don't know sh!t from clay.
A bloke here in NZ does those plates too. Apparently the hard part is getting all the numbers stamped in a perfectly straight line.

Although I am sure that the idea of a compliance plat that has different details other than what the manufacturer intended might look very good when showing a car, If you attempted to register the car with a plate like this fitted it will become a matter for the courts if you are caught. It could become a legal nightmare. Not to mention that there are cops who are members of this and other forums that are reading your intentions.

Talk about a shady deal.

Nothing illegal about this plate as it is not a compliance plate.

is this still on? i'd get one i saw them on ebay a little while back

I just want a stock one. my ute has one missing. any idea if they are illegel or is it just an I.D. plate re print?
I'm not looking to change anything on it.