Just a quick google search gave these options:
QA1 R101-200: Mopar Rear 6-Link Suspension Conversion 1967-79 Mopar A-Body with 8-3/4" Rear Axle | JEGS
4-Link MOPAR Coil-Over Rear Suspension Systems | Control Freak Suspensions
Prolink Rear Suspension for A, B, C, and E-Body Mopars
Mopar Pro...