Over filling keeps the input bearing wet and last a lot longer. I put over 300K towing miles on my Getrag 360 with a couple rebuilds.
I would fill it up to the fill hole then pull the shifter and add another quart.

72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, .
Moparmarks Parts & Restorations
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Grand Jct. CO
970-261-7039
http://moparmark.com/
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