What is the grid total for bruce mclaren with over 73 laps?
CREATE TABLE table_56764 (
    "Driver" text,
    "Constructor" text,
    "Laps" real,
    "Time/Retired" text,
    "Grid" real
)
SELECT SUM("Grid") FROM table_56764 WHERE "Laps" > '73' AND "Driver" = 'bruce mclaren'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the grid total for bruce mclaren with over 73 laps? ### Input: CREATE TABLE table_56764 (
    "Driver" text,
    "Constructor" text,
    "Laps" real,
    "Time/Retired" text,
    "Grid" real
) ### Response: SELECT SUM("Grid") FROM table_56764 WHERE "Laps" > '73' AND "Driver" = 'bruce mclaren'