Found an AfterMarket ADDCO rear sway bar for 73 & up trucks.
Not sure if it is still available.
hope its useful...
ADDCO #020-202
1'' Rear Sway Bar
1973-91 Blazer 2WD/C-10/C-20
1973-91 Blazer K10 4WD/2DR Tahoe/Yukon
1973-91 Blazer K20, K30 4WD
1973-91 Suburban/Yukon XL 4WD/1500
1973-96 Suburban/Yukon XL 4WD/2500/3500
1973-87 C10/C20/C30 2WD/4WD
http://www.jegs.com/i/ADDCO/020/202/10002/-1
ADDCO :
http://www.addco.net/aftermarket.htm
ADDCO Distributors (per their website)
http://02bbfb5.netsolhost.com/distributors.htm