1000 Horsepower
One thousand hp with a VP44 pump is possible, but only a handful of people in the country have done it. Those that we know of just smile and say it is the same as the 750 hp with a few "special tricks." As to what those tricks are, no one wants to say.
We would assume that the injectors probably need to be custom extrude honed to handle the fuel requirements. Multiple stages of nitrous need to be utilized to help fully burn the massive amount of fuel the injectors inject. The nitrous also helps reduce the exhaust temperatures which, at this level, could get out of control very quickly.
Lowered compression is usually required. Somewhere between 14:1 to 14.5 seems to be a popular range. We would also suspect the pistons have been ceramic coated to help handle the heat. ARP 625 head studs are strongly recommended. The rest of the modifications that are needed, or rather tricks, well, who knows but the select few who have done it?