Here's the production numbers breakdown for BB coupes vs convertibles. Not many L78 convertibles, like that is a surprise.
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L35 396/325hp
67: 3432 coupes and 571 convertibles
68: 9841 coupes and 932 convertibles
69: 5667 coupes and 785 convertibles * thru Sept 69, missing Oct and Nov production
L34 396/350hp
68: 2371 coupes and 208 convertible
69: 1769 coupes and 198 convertible * thru Sept 69, missing Oct and Nov production
L78 396/375hp
67: 1025 coupes and 113 convertibles
68: 4413 coupes and 162 convertibles
69: 3400 coupes and 200 convertibles * thru Sept 69, missing Oct and Nov production
*updated with L34 info that Bryon posted.