What regs are you working too?
Ultimately the answer is 'yes'. You can do this. But it
may impact the class you compete in.
The ALRC regs are purposely written, that if it doesn't say you can do something, then you can't.
Section A - General A .1. As a general principle in all vehicle regulations, it is prohibited to carry out any tuning or modification that is not specifically permitted. The fact that some modifications are mentioned as prohibited does not imply that others are allowed.
There is nothing in the regs which says hybrid or VNT turbo's are allowed.
However under the Modified class regulations it says this:
C.3.2. Carburettors may be changed, air intake system and manifolds may be altered to any specification.
I think you could argue the case that a turbo is part of the air intake system. However, this is a little ambiguous, so may require clarification from the Scrutineering committee should you encounter resistance.
In fairness, being modified class is probably correct. A hybrid or VNT turbo should be giving you more potential power over a wider powerband. Therefore giving your vehicle a better chance of making a long climb, that others may fail. i.e. you are getting a competitive advantage out of the modification, which is the entire point of having a modified class!
Sadly, some see the "Modified class" as a dirty word and would rather lie and cheat to remain being called standard class. This isn't something I would suggest or promote, despite the fact a club scrutineer will not be taking your turbo apart to inspect it on competition day. There is a little thing called
honesty and
integrity.
For club level trials this probably won't matter, as most clubs will amalgamate standard & modified classes anyway, unless it is a particularly large event.
If your local scrutineer is unhappy with the above, then there is also class-Q. Which basically allows anything that looks like a Land Rover with a Land Rover engine/gearbox.
Class Q. A vehicle manufactured from Land Rover parts in accordance with MSA Regulations. Vehicles must retain Land Rover axles, engines and drivetrain. Vehicles must retain the appearance of a Land Rover.
https://www.alrc.co.uk/stylesheets/downloads/Competition-Rules-and-Regulations.pdf