I cant claim any credit for that one! I think its custom but I did see something similar on defender driving around town so possibly there its a product on the market somewhere.
The biggest challenge I'm finding for 'know how' is, surprisingly, getting good pertinent info on the GM side of the project. I can type any rover related query into google and get a number of good on topic forum posts very easily. Anything I try to find out about GM via internet search nets me several identical pages of online aftermarket parts stores and crap, but its very hard to narrow it down to the info that I'm actually looking for