something i ran upon:
http://kmhafer.datsun510.com/Subaru.htm
Clutch-Pack LSD:
1985-1986 (production up to 3/86) XT 4WD is listed with a 3.70 LSD option (Subaru part # 7220 11000).
1986-1987 (production from 4/86-10/86) GL 4WD is listed with a 3.70 LSD option (Subaru part # 7220 11001).
1986-1991+ (production from 11/86) Loyale/GL 4WD is listed with a 3.70 LSD option (Subaru part # 7220 11002).
1988-1991 GL and XT-6 4WDs with single range transmissions are listed with a 3.90 LSD option (Subaru part # 22011 GA022).