No experience here with the lowering springs but I just replaced all 4 springs on my car with Eaton stock height springs. It raised the front 2 1/4 inches and the back 1 inch so I'm assuming my springs were pretty worn. For reference the pics below are how it sat/sits before and after.
And FYI, from the Eaton website, for 70 vs 71 the part numbers for the rear are the same, the front are different. Also, bear in mind, my car gained about 120 pounds with my drivetrain swap.
Before:
After:
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70 TA, 467 cid IAII, Edelbrock D-port heads, 9.94:1, Butler HR 236/242 @ .050, 520/540 lift, 112 LSA, Ray Klemm calibrated Q-jet, TKX (2.87 1st/.81 OD), 3.31 rear
https://youtube.com/shorts/gG15nb4FWeo?feature=share