I want to do the 63 in or 64 in chevy leaf spring swap with the shackle flip. What I don't understand in the thread on TRS is....Why were they re-arched 12" and doesn't that shorten them. Were they re-arched for more lift or what?

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2010redfire-
2010 Ranger Sport 4x4 Redfire Red, stock 4.0, 3.73 gears, Putco bed rails, Line-X, Truxedo bed cover