Not sure what you're trying to do here... are you trying to turbocharge the 3.0? Mitsubishi made a version of the 6G72 that was twin-turbocharged, with DOHC heads, for the 3000GT/Stealth, but I don't think that the work will be worth it. If you have access to a 2.5 T1, you would be able to make more power much easier, IMO, by swapping one of those in and throwing a TII intake, intercooler and electronics on it. You will almost certainly kill your transmission if you have the A604 with either turbo engine. A minivan-spec A413 will be more than capable of handling the power of the 2.5 TII. I forget exactly where I saw it, but there was someone out there running ridiculously low times with a very slightly upgraded A413 in a Reliant wagon. The 4 will also get better fuel economy than a turbo'd V6 as long as you keep your foot out of it. The setup I describe is pretty well documented by the turbo van drag racing crowd.