Found this on line, Production numbers

[Mr Chevorlet]

PRODUCTION

1967
C10 long-box fleetside -- 165,973
C10 long-box stepside -- 19,969
C10 short-box fleetside -- 43,940
C10 short-box stepside -- 45,606

1968
C10 long-box fleetside -- 204,286
C10 long-box stepside -- 18,632
C10 short-box fleetside -- 46,483
C10 short-box stepside -- 46,322

1969
C10 long-box fleetside -- 268,233
C10 long-box stepside -- 18,179
C10 short-box fleetside -- 54,211
C10 short-box stepside -- 49,147

1970
C10 long-box fleetside -- 234,904
C10 long-box stepside -- 11,857
C10 short-box fleetside -- 40,754
C10 short-box stepside -- 40,754

1971
C10 long-box fleetside -- 206,613
C10 long-box stepside -- 7,269
C10 short-box fleetside -- 32,865
C10 short-box stepside -- 19,041

1972
C10 long-box fleetside -- 273,249
C10 long-box stepside -- 7,538
C10 short-box fleetside -- 39,730
C10 short-box stepside -- 22,042