I have a 07 supercrew with the trailer package, I have just installed the groundforce shackles and shims at the 2" hole. It is still sitting about 2" higher in the rear. I believe it has blocks off of the 4wd, does this sound normal, is it ok to take these out. heres some pics

 

I know that the 04-06s only had the blocks if you had 4WD. On my previous 04 SCAB, I tried the GF shackles and didn't care for the way they changed the rear spring rate. I removed them and pulled the spacer blocks and installed the 2WD u-bolts. I drove it like that for about 10k miles before returning it to stock to trade it in. I like the fact that removing the spacers doesn't mess with the pinion angle like shackles do. That picture of the spacer looks different than the ones that I've seen on 04-06s. Is your truck 2WD or 4WD?

 

Truck is 2WD

 

Hmm, they must be putting those smaller blocks on 2wd's now.