Was the 77 estimate perhaps derived from the 'Engine production by Suffix' listings Fran Preve had?.
From what I remember of conversations I had w/ Fran his listings showed Tonawanda engine production by Suffix and he used to consider about 95% of the total were put into assembly line cars and the remaining 5% kept for service/warranty etc..
So if Engine production by Suffix was 81, assembly line production at 95% would be about 77 units?.
~ Pete