Here's a couple of things to think about
:
Do your research on the backspacing on your rims. I know from experience with the stock 17" rims (5.5" backspace...if I recall) that moving up to a 37x12.5 caused a bit of rub on the front stabilizer shaft at full lock. Going to a 37x13.5 would be worse.
Regarding the torsion keys; I've found that cranking the torsion keys too much - like, if you're trying to 'level' the truck - will make your ride pretty harsh. Bumps will be much more pronounced and the steering will feel a bit squirrely; you probably should also have your alignment checked if you crank them way up.
IMO...and the best thing I've found is to go with the Cognito Leveling Kit. It gives you different upper control arms and other bits that will lift the front but also keep the ride in tact. It alters the geometry of the front suspension so that the truck will sit level but ride like stock. When I did my first H2 I got their complete kit which included Bilstein 5100 shocks...it was perfect. Then you can use the torsion keys to make subtle adjustments (0.25-0.50") to get the height just right.
Regarding the coil spring swap, I'm pretty sure you need the seat (or spacer) check this link for more info:
http://www.clubhummeroffroad.com/for...ht=coil+spring