I think that is higher than most oils but not quite the optimal amount as researched by the Classic Car Club of America. They produce their own brand of oil with 1600ppm ZDDP.

I've been using T4 for years but was recently told that they had reduced the amount of zinc in it. I believe it used to be around 1400ppm but I don't remember now. I'm glad to know you got the straight dope from the manufacturer.

Here is a link to purchase Classic Car Motor Oil and read more about ZDDP in oil if you wish.

https://inrccca.org/product/classic-car-motor-oil/

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)