Thrust Buttons - Do I need them?

I was taking out the center section of my 8.75 rear end (for my E-body Cuda) to install it in a new 'B' body rear end I purchased from Dr. Diff and found the thrust buttons sitting in the bottom of the old case. I didn't know what they were at the time so I went ahead and put the new stuff together without them. Do I really need them in?
Thanx.

If it`s a power lock sure grip and you`re using original style tapered wheel bearings you will never be able to set the axle end play without them.

Do you have green bearings? If so, then you don't need them. Otherwise, yes you need them to set end play.

Yes the new rear end came with green bearings.

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Yes the new rear end came with green bearings.

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then you don't need them , but i would save them as a just in case