I have an 08 f150 fx4 with a 6" lift. I'm gonna go with the bilstein 5100 in the front and a 2" strut space in to front to get me up to an 8. On the back end there is a tapered block. Do i need to remove that block and get a 3" block or keep it and get a 2" block?

 

If you are going with the 5100 leveling shocks then you do not need an additional spacer, let the preload give you lift, dont try both. Second, what size is the block in the rear now, i guess by deduction 1" so I guess you have a different set of leaf springs? If you are talking about stacking do not do that, get whatever block you need to get back to the correct ride height. Tapered helps keep drive line angles in tolerance.

 

^^ this. bilstein set at 2" = no need for 2" spacer.

for the rear, i'd either replace your 2 blocks with 1 or try and find a large AAL

 

I just got done with my lift, I have an 04 screw and just installed my 6" procomp lift with billstein 5100.I was gonna add 2" more to my lift but was told that I would run in to problems,so I left it alone ,even without adjusting the front strut I was still 2" lower in the rear so I installed 1.5add a leaf and 4-1/4 " shims on each side to give me a total of 2 1/2" on each side , I had to get some longer u bolts made at a spring shop.and longer centerbolts for the rear center bolts . I will post a picture of my rear asap....so total in the
Rear is aal,shims,factory block,procomp block