Think your right mate the more I look at it that is a home made effort and not the factory part.
I'd love to find the factory one but it must have been such a rare setup.
It's a adjuster bolt that pulls the idler pulley upwards to tension the belt. Sadly the parts are discontinued as strangely I'd like to run this setup to keep AC but go electric power steering to get the air filter behind the drivers headlight.
This is a 3G kit that was produced in collaboration with Dave Burwash when he was running TMD.
I have a new pair if brake lines if the buyer of this kit would like to replace the worn lines happy to sell cheap.