My 69 convertible shipped with 4 leafs, and new 4 leaf replacements had rear end drop 1.5" from spec ride height. I bought the Classic 5 leaf for this VERY heavy bird (400, air, power everything, auto) and it restored the ride height to proper level and did not add excessive stiffness because of the high sprung weight. A light, low option coupe will weigh less and need less spring rate.

Bad news: the Classic 5 leaf shipped with the wrong spring pads, so I had to reuse the ugly ones.