The format you indicate is a little confusing to me. Should be in the form
aa mm dd f s. Where
aa is the axle code, in your case PJ;
mm is the month,
dd is the day,
f is the plant, and
s is the shift - either a 1 or a 2 for first or second shift.
Assuming, from your username, we're talking about a '68 -
For either '67 or '68 model year; PJ decodes as 3.73:1 ratio, 12 bolt rear end, positraction (If this is a '69 axle, PJ decodes as a 2.56:1 ratio, 10 bolt, posi rear end)
G = Detroit Gear and Axle Plant; 1 = 1st shfit
I'll defer to others as to what the 2 at the beginning or the 88 at the end mean.
Also check the CRG axle decoding section at the following:
http://www.camaros.org/drivetrain.shtml#RearAxleNumbers
