I agree, you won't be getting 1500 hp out of a 1uz, a 2/3 uz maybe, but its pretty well established that they crack blocks.
As for trying to re invent the wheel, don't, N2O has been used since ww2, and for good reason, it works. It also has more benefits than just being a powerful oxidising agent, when it breaks down into O2 and N2 it releases a whole bunch of energy from its chemical bonds, which is the main reason why it is so good at spooling up massive turbos at the staging lights.
And as for a hilux not being strong enough...
I would use E85 as soon as it become widely available here. In Aus it seems as though its fairly consistant at the pump at around 70 % ethanol, and there are many high power cars that just tune to this level and be done with it.
I'm all for having BIG power, but on the street a genuine 400 rwhp will be more than the tyres/road can handle.