Hey, I'm not too far away from you. I'm just at the end of the 71. Anyway, I would keep the original shackles on. Also, by jacking up the rear, you're putting your weight higher which can make the car more difficult to drive around a corner.
this is very true after i put the SS combo on mine. i had to completely rebuild my front end. front suspension was just too worn.
i installed complete new shocks & MOOG new front end. bushings, rods, arms. etc.... feels like new car now. :coffee2: