You don't HAVE to...but you won't be safe if you decide to hammer on it hard.
60# valve springs are cheap insurance.
I would strongly recommend it.
-R.J.
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1998 2500 QC SB 4x4 White DDP 4s, O-ringed "cool" head, HT 64/12, Full Garmonized SunCoast, billet front to back, 4" straight pipe to 6" miter cuts, pump plug, no plate, AFC disabled, 5K GSK, far more to come.....