Hey, I don't really think it will take all that much to get to 7-800 hp. I think a 13mm pump, a big charger and some 5x20' with custom lines would get you real close if you can get the rpm's out of it. Porting as stated above will help as well. Remember CDS is now the only place for good parts, Hypermax and Scheid do a great job, and their prices are near or less. There is a reason 80% of the tractors have this motor, and it's because its the 12 valve 6bt of the tractor world. I would love to see your progress!
And depending on your donor motor these things had lower compression than our trucks do. I think my dt360 has 18:1 to start with. If you are pulling the motor apart, Hypermax does their magic for 125 per piston.