How much horsepower to the ground?
 

I know the 5.7l hemis have 345 horsepower, but is that rear wheel horsepower or is that at the crank?

290-310 range depending on vehicle specs (2 or 4 wd, standard cab, extended cab, short bed, long bed, etc)

4X4 Quad cab

Any shops in your area with a dyno? They usually have a "Dyno Day" a few times per year with a special price for one or two pulls. That's the easiest way to know what power you're putting out. Run it in 2WD, I don't know if 3rd or 4th gear is 1:1 on yours. The shop should know. :)

Third gear is 1:1, four and five are O/D. 345 is at the crank. I suspect it's < 275 to the ground.

345 at the crank, generally it's 270-290 with the driveline loss at the wheels.