C-43 no relation Boeing 7x7 series
The first generation "Original" series: the 737-100 and -200, also the military T-43 and C-43, launched February 1965.
The second generation "Classic" series: 737-300, -400 and -500, launched in 1979.
The third generation "Next Generation" series: 737-600, -700, -800 and -900, also the military C-40 and P-8, launched late 1993.
The fourth generation 737 MAX series: 737-7, -8, -9 and -10, launched August 2011.
no relation