I know which vendor this is coming from, I spoke with them about a week ago and this was brought up so I'll chime in, but since Unabomber does not disclose who, I won't either, in regards.
BUT, as keanie says, a twin-turbo design could be called for possibly.. I know I've seen a couple custom built EJs with a twin turbo design, not to say that they'd make a whopping load of power like what this guy wants.. but its a start towards something. If Supra's can do it on an Inline-6, then can it be done on an H-6, sleeved and closed? These guys are highly reputable and based on that and my experience, can imagine they're well up to the ask as they seem. As usual.