you never want to use brakes that are not matched same on each axle.
BOTH rears need to be the same, or Both Fronts, it's not important that front and rear match.
so to answer your question, NO do not just put the one ate on with the existing bendix in place.
you need to either rebuild your bendix and put it back, or order another ate so you have a matched pair on your rear axle...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!