Castle HV Hydra, but where is the car version!!!!

[Dagger Thrasher]

That's a very good point...if it was simply a case of reprogramming the Hydra and whacking on a heatsink, Castle would have already done it IMO...or be in the process of doing so. It's probably nowhere near that simple. The MGM controllers are most likely designed around handling what a car dishes out primarily, and then has alternate software for boats. The Hydra controllers are primarily boat controllers, and I'll bet cars put a bigger strain on ESCs than boats do.
As for voltage... around 40V and above can kill a person if they directly contact it. So it's never going to be a setup that a lot of people use...