I know that some registration inspectors are not the sharpest tool in the shed but you are looking for one that is downright stupid.

Even if you get the vehicle registered by subterfuge, you will come to grief once you smash it because the smart ones will ping you for operating a non compliant vehicle, & therefore unregistered, & the insurance company will wipe you like a dirty fundamental orifice.

Why on earth would you want to use an engine that must surely protrude as far back as the dash facia?
Any further forward & the balance ratio must surely be compromised & yes, there's a regulation about that too.
If you add weight to the rear in order to redress the imbalance issue then you are defeating the purpose of using a small & light car in the first place.

If this is to be a race rocket, then you don't need registration anyway.

You will also need a valid weighbridge ticket for registration so that they know how much to tax you, so if your claimed weight & the actual weight don't link up as they should, then you are 'sprung'

I think that Pepper has it. This sounds like just another ill conceived project that end up either as scrap or as an unfinished project on eBay.

There is a 1200 coupe on Youtube that is capable of 7 second passes down the quarter with a Nissan 4 cylinder engine.
The point?
If you can't frighten yourself totally sh1tless with any number of Nissan 4 cylinder engines that can be legally fitted to a 1200 Ute then you're just not trying.