I've always thought this^^^was the best case best all Toyota fix, but haven't afforded the option in my builds. If cost and time were no concern, then this is what I would stick back there.... Now if a guy were to relocate the hangers, then the questions of which springs to run goes right out the window because it's open season for choice. I have always thought the best real-world case would bear availability and cost into the equation...once you undo the shackles of factory hangers, then the gloves come off and anything is "possible"...you could EASILY run 60 series- or whatevers- fronts and rears, or rears, or fronts at all 4 points while keeping things like driveshaft lengths and fenderwell clearances and etc. etc. where they need to be. But short of mixing bits of 60 packs into 55 packs, or relocating hangers, I don't think the US owners have alot to gain from use of a stock 60 series spring.