How do '86 k30 front springs differ from the '88 V30's?

[Chevy3+3]

I am thinking about putting an add a leaf into my current front spring packs on my '88 V30 and I see alot listed for up to '86 & '87 being one part number and the add a leaf kits for the '88-91 V series are a different part number. I just wondered if anyone might know what the difference would be. The reason I ask is because there are fewer manufacturers for my '88 and Summit sells a Skyjacker add a leaf kit but lists it for useon vehicles up to '86.

Thanks