From GM Canada's "1966 Corvair Equipment" report, we know that 237 1966 Canadian Corvair Corsas were equipped with a turbocharged engine (RPO L87). What that report does not tell us is how many of those were coupes and how many were convertibles. Fortunately, however, we do have enough more info about 1966 Canadian Corvairs to make a reasonably-accurate estimate.
Dave Newell visited the GM Canada archives in 1991-93 and made copies of selected pages of their vehicle production records. The 14 pages that Dave copied account for 863 of the first 2052 Corvairs produced in 1966. This represents 14% of the total 1966 Canadian Corvair production of 6137.
Of these 863 Corvairs, Dave counted 33 turbo-equipped cars (3.8%): 20 coupes (2.3%) and 13 convertibles (1.5%). If we apply these percentages to the total production, we get 141 turbo coupes and 92 turbo convertibles, for a total of 233 turbo Corvairs for 1966. This projected total agrees quite closely with the known figure of 237 made, so we can feel pretty good about the reliability of Dave's sample.
Of the 682 Corsa coupes produced in Canada for 1966, 141 with the L87 option is 20.7% of production. Likewise, 92 turbo engines among the 211 Canadian Corsa convertibles produced in 1966 is 43.6%.
Because Dave's sample is from the first third of production, we can not tell for sure whether the proportion of coupes to convertibles remained consistent throughout the model year. Only a sample that was more evenly distributed throughout the production sequence could validate our current estimate.
Data from GM Canada's "1965 Corvair Equipment" report
In February, 2006 Dave Newell noticed that his copy of the GM Canada end-of-year production report for 1965 Corvairs, unlike the one for 1966, breaks down the RPO L87 total by coupe and convertible. Of the 560 Canadian turbo Corsas made in 1965, 443 were coupes and 117 were convertibles.
Dividing 117 by 560 yields 21% convertibles. If this percentage is then applied to the 1966 total of 237 Canadian Corsas with L87, that yields only 50 convertibles with L87 in 1966, not 92.
Of course, there's no way to know what the real number is unless we gain access to the GM Canada archives and count every car. The 1965 figure does tell us that our estimate of 92 Canadian turbo convertibles built in 1966 is not a low-ball figure and in fact may be on the high end.
Many thanks to Dave Newell for doing this research!