From the 88-93 light duty 3/4 ton pickups. Preferably later ones because they'll more likely have abs.
Hmmm...I could be wrong, but I don't think rear matters with ABS...b/c your rig has the ABS module, I'm not sure how the rear drums could affect that...anyone?
It can be tough to find the 6lug variant...so start looking months in advance!!