It's usually a Sure Grip or True-Tack diff, not a possi in a Mopar product {Eaton, Richmond or DANA corp.}
for strictly drag racing 2-2.5 qrts is about right, I always buy 3,
it kind of depend on what type/style/capacity pan it has too,
& whether it has a spool or a diff. & what type/style of diff. or locker,
some people/mfgrs recommend different weight oils, thicker for hotter temps & thinner for cooler temps,
also a spool takes more oil to fill up to the drain plug, you can also use lighter weight oil too,
{some recommend only run a single qrt for strictly drag racing usage, I never did that}
but IMO for the street/strip, just fill to the bottom of the drain plug, make sure it's a on a level surface
IIRC could take almost 4 qrts in my Dana 60's full floaters in my truck... don't quote me on that
make sure to get the proper weight gear oil for the style of diff. it has
I use Royal Purple Max Gear 75/90 or 75/140 synthetic
depending on what kind of diff, the 75/140 is what allot of mfgrs will recommend for a Dana 60