Opinions wanted for replacement Rear Spring selection. Thank you

The Jaundiced GT ('71 Dart GT) has ManciniRacing 2800lb springs on it. They were installed over 21 years ago (by the previous owner). The car also has the factory installed 8 3/4" rear end with WheelVintiques 15" X 7" (4 1/4" backspace) sbp Rallye wheels with 245/60R15s (with room for 255/60R15s (next time)).

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