I was asking myself a question that I'm sure everyone has wondered about. Why is it that a 5.9L cummins can achieve nearly double the torque of a 6.5with relatively minor mods? I know that the cummins has lower compression which allows for more boost (32 lbs is what banks claims on their power pack), but given the fact that the 6.5 has a higher compression ratio, it should be able to produce the same torque and hp with LESS boost than the cummins...right? Is there anyone who has gotten over 600 lbs torque from their 6.5 with stock pistons and internals?

Give it the fuel and boost and the 6.5 will give you whatever you want as far as power, how long it will last is the source of much debate. While theoretically trying to compare apples to apples you would also need a really really good intercooler. Also torque comes from a combination of bore and stroke leading to volume. which the cummins has the largest of any light duty diesel per cylinder, that's where those great torque #'s come from.

700 ft lbs is probably the top end of what a highly modified 6.2L/6.5L would make, based on bill heaths tt.

Lowering the cr will allow you to up the boost and have the same overall cylinder pressure.
Lowering the cr .010" with the over head gasket,change the cam, increasing valve duration and overlap to increase volumetric flow and using a slightly larger turbo with an IC should help to increase the sustained boost levels, and increase the o2 density top end while not totally gutting bottom end power or cold starting.