How much will i need to machine off a 3" block.(taper) For proper pinion angle? runnin stock springs on a 89XJ.Hey they were free..and im cheep.

 

cheap is not always good, and well block will damage your leafs quicker , and well your angle will be off, if you fix that, your leaf life will still be shorten..

 

Blocks are not a good idea.
They will cause spring wrap and damage your spring rather quickly.

I am assuming that you are planning on doing a lift with the blocks and are concerned about pinion angle, is this correct?

 

Blocks are bad for your suspension. You will de-arch your springs in a very short time. Use some shackle extenders or a new set of springs. The blocks are great for about a week then the de-arching begins and your current springs are trash when that happens.