1st Generation - 240Z, 260Z and 280Z
The first generation Z was known as Nissan’s Fairlady Z in Japan, but was introduced to the US markets in the fall of 1969 as the Datsun 240Z. This vehicle, designated by its Nissan code name, the S30 featured a 2.4 liter engine that produced 150hp with a 4 speed manual transmission.
The 1st Gen Z would come to encompass the 240Z, 260Z and 280Z.
Names and actual manufacturing dates for these cars varied by country but we will focus on the US market.
Here is a nice article on How Stuff Works...
The 240Z was introduced in 1969 and was manufactured thru 1973.
240Z Production Numbers
1969 - 3
1970 - 17,005
1971 - 40,219
1972 - 60,025
1973 - 51,332
In 1974, the engine was enlarged with a longer stroke to 2.6 L resulting in the 260Z.
53,451 260Zs were manufactured in the only year that the 260Z would produced.
1974 also so the introduction of the 2+2 model.
In 1975, the engine was once again enlarged but this time by increasing the bore and therefore the cubic inches of the 2.6 L engine to 2.8 L resulting in the 280Z.
280Z Production Numbers
1975 - 54,907
1976 - 63,690
1977 - 56,072
1978 - 62,699
Wikipedia also has some good information...