Well....you are only working with 222 or 223 cubic inches here.
It is close to optimum output for a two valve engine designed more for low rpm torque output.....if I remember correctly, horsepower is at 210.
Not to shabby for its dispacement......I don't know its torque rating but I'll bet it is in the 250 ft lb range.....again, fairly respectable.
More aggressive camshafts could eek out a bit more power but that would occur at a higher RPM.....not very useful in a truck application.
So, what I'm getting at is there isn't a magic bullet that currently exists to make more power and torque without changing the characteristics of the engine.
The lower gears (higher numerically) would provide a bit more 'snap' off the line.
The QT II 3.7's used 3.55's and these could be a direct bolt in with a computer reflash to recognise the gearing.
As far as intake or exaust changes the odds are there would be little change with exception of operation at the last 1000 RPM before redline......there might be a bit of restriction at those high cfm requirements but the butt dyno likely would not be able to feel it.
So, gearing or jack up the radiator cap and slide a V-8 Commander under it are, in my opinion, your only options.
All the 3.7's are the same, whether installed in a Commander or Liberty or Grand Cherokee.
The 3.8, found in the Wrangler, shares nothing with the 3.7.