The Holden HD sedans and station wagons were released in February 1965 with coupe utility and panel van body styles following in July of that year. The HD range replaced the Holden EH series which had been in production since 1963. The HD had a completely new body, which was wider and longer than that of the EH and offered significant increases in passenger space, load space and equipment levels. Disc brakes were offered for the first time on a Holden model and the optional Hydramatic three–speed automatic transmission as used in the EH was replaced by a Powerglide two– speed unit. The HD was also the first Holden to be offered with a factory performance engine option, the “X2”.
Source: Wikipedia, 2011