How much HP and Torque can you gain w/o turning your 4.0 into a stroker?  

There are SOOOO many differant variables to that that I don't think anybody could tell you for sure.

Christian did an article in last month's issue (March 07), figure if you added an intake, throtle body, exhaust, coil packs, throtle body spacer, cam, and aluminum head you can figure on adding about ~75 real horse power. Then you can add a supercharge which is good for about a ~45% increase at the wheels. And if you still want more, there is always NOS.