Ok this is the first f150 I've had that was lifted. Its a 95 that has a 4 inch lift the rear has two 2 inch blocks stacked one is factory and the other isn't. I want to do away with both and have just leaf springs what size do i need 2.5, 4 or 6 inch lift springs. Thanks

 

you need the factory block, that block is what gives the rear axle it's proper driveshaft angle

 

I would guess 4" if you want it level, and 6" if you want a man-rake. And like tjc said, check that block to see if it has a taper on it for driveline angle.

 

The factory block has no taper its flat the springs i was looking at have a little wedge on them

 

I replaced my two block setup with a solid 4 inch block yesterday and it messed my pinion angle up bad. So today I took angle finder took some measurements.
I took the 4 inch blocks out and put my factory overload block back in with non tapered 2 inch blocks. This put my pinion angle 1 degrees higher than my transfer case. After measuring everything i came to the conclusion that my pinion angle was off to begin with.
I'm pretty sure I can get everything right where it needs to be with 4 inch lift springs with a 2 degree shim turned backwards on the leaf springs.