8 3/4" Third Member Swap Questions?

Hello,

I have my self totally confused. I had a shop replace my 1965 2.94 open third member with an unknown year 985 (742?) 3.23 open third member. The 985 unit was out of a tapered axle differential. I have not been back to the shop yet but before I go I have questions about the Thrust Blocks (buttons).

I know I have them on my limited slip 3.23 third member in another car, I installed it myself years ago however the more I read the more I don't understand open third members. It appears that all Mopar 8 3/4 third members have thrust blocks? I pulled the 985 3.23 open third member out of the differential and do not recall seeing any thrust blocks, did I miss something or did I drop them and lost them? However I was not the first person to have been in the differential, the person I got it from had pulled the axles to verify the gear ration on the ring gear, then put the axles back in the housing.

Tomorrow I am going to pull the wheels and see if I can check the axle end play. I know the 1965 differential adjusts with an adjuster ring and not shims like the old tapered axle differentials.

The following was copied from the Internet:

Any 8-3/4" center section may be interchanged for another as an entire assembly, with the exception of center sections manufactured prior to model year 1964 (See Section 1: "Thrust Block Variations").

There was a difference in thrust blocks prior to 1964 that make center section

interchange, as well as axle interchange problematic. The thrust block, or "axle shaft

thrust spacer", it thr block that both left and right axles butt up against inside the center

of the differential. Prior to 1964, all open differentials used a thrust block was

approximately 1/8" to 1/4" thicker than units made after 1964.

Any suggestions other than checking the axle end play would be appreciated. Did I make a swap that should not have been done and go back to my 2,94 gears?

Thanks

Dennis C.