Join Date: Jul 2004
Location: DC burbs, MD side
Depends on your spring length and how much you intend on dropping the car. With a 10" 375lb spring in front, stock height, I do not need helpers. That is, at full droop there is no compression in the springs, but no slack either (pretty much perfect). If I went to a 10" 425lb spring, I would have to lower the spring perch to get the same ride height, and at full droop there would be some slack in the spring, and I might choose to install helpers. Likewise, if my spring length changed, e.g. if I needed clearance to the inside of the rim, it would change the setting of the spring perch, which might create slack at full droop.
Glenn may chime in here about helpers, or you can do a search, because I know he's posted about them sometime in the last few months.
That's a pretty stiff rear spring...you gotta TA or 3-link?