Just found the info on the transmission.
In Buick service bulletin #65-4, dated January13,1965, it reads
"A second Gran Sport option, Code"A3", will include all of the items mentioned under Code "A9"above, except that a 4-speed fully-synchronized floor shift transmission, again with heavy duty clutch, replaces the 3-speed fully-synchronized transmission. This 4-speed transmission is the same heavy duty unit now available in the Wildcat models when a 4-speed transmission is specified."
Loren