SQuattin on my hind legs. got blocks.. airbags cummin, but questions first

[HarleyPhreak]

Hey boys, after surfing a few truck shops and getting different answers and suggestions from each shop, i fugure id come here and get to the bottom.
I have a 06 f350 with a 6' BDS lift, but from what it looks like, the previous owner removed his rear blocks and airbags. i know they where there due to the airbag brackets all left behind, and the fact the wheel well gap is much bigger on the front end. I purchased Ford blocks measuring 3.75" but my main question is: will i need a spacer for the drive shaft with a block this size.. ?? each shop tells me a different story. i got the blocks at a local 4x4 shop used, sitting on the shelf.. came with no ubolts or instrucxtions.. they look to me like a genuine ford part cause the ford emblem stamped on the top.. in what situation would a stock ford truck have blocks like this?? im kina confused how this could be a stock part.
Any help boys? feel free to add any tips . my mechanical skills are pee wee level, but with your help, tomorrow im gathering up all the parts i need and install the mutha****a myself friday (my day off, supposed to be nice out

let me try to post a pic of my block
thanks hommies

[HarleyPhreak]

pic of the block.... 3 3/4"

[GregsSD]

That is a factory block, F-350's came with 3.75" blocks in the rear and F-250's came with 2" blocks.

If that picture is the way your truck is sitting with no blocks, then you must have lifted springs in the rear and adding those blocks to them would be way too much!

measure the exact difference in height between the front and the rear because it looks to me like you would only need 1" or 2" blocks to bring the rear up.

[HarleyPhreak]

U got it bang on.. it has raised leafs. But the airbags where yanked out... I think your right, im no longer going to use those blocks... way too much.. i said **** it and went and bought some firestone air bags today $422 after taxes. if this doesnt get my desired height, then i'll go out and grab another set of 1 or 2 inch blocks... as for now i have an extra set of 4 " blocks i no longer need lol... its up for grabs if someone wants it
i'll go to town tomorrow on it...
Air bag guys, give me some do's and dont's to help me through my install tomorrow... every and any tip might help a wannabe mechanic like myself.. i always screw it up or takes me 10 hours to do a 1 hour job lol