Try and find an IP from a 3.5L 603 as it has 6mm elements. Like mentioned above the most you can do before sending it overseas is adjust the full load and put a bigger turbo and an intercooler.

disregard this info, I researched it and the 3.5L pump does not have 6mm elementes the 606 electronic IP does so if you can swap the 6mm elements to the 603 pump and get it recalibrated you'll be good.

With an IP from a 3.5L 603, would it be better to go with the HX35 turbo or the HX40?

I figure 200 HP with 300 ft. lbs. of torque is what could be expected if the IP was dialed in correctly?
I just didn't know if there was a little bit more that could be gained by performing a few other tweaks.