I put one on each end of my '36 3w. The rear actually went up because the original spring was both tired and had a cracked leaf. I ended up taking off the two top spring leaves to adjust, put them on the bottom to act as spacers for the clamp/u bolts. You have to order the "hot rod" or after market shackles. These come in two lengths, the shorter matches the length of your stock shackles, the other is the shackle for the '42-48, they're about 5/8" longer if I remember correctly and will give you some additional lowering. Posies sells the Pete & Jakes version of these. The buttons really help the ride IMO.