Use your stock center pin as well unless it’s broke
But that other pack also is missing the plastic sliders that keep the springs from gouging into the keepers near the end of the leafs.
I’d send that wrong back and see if you can get the right one like the other. I wouldn’t doubt if spring rate is different too
I guess I never thought about using the center pin that's in my stock leafs. Funny thing is the picture of the product on Dormans website shows no metal spacers between the leafs or the plastic sliders near the ends either go figure, and it's identical to the one.