How can one tell which 5-speed tranny in a 1980?

[Kerrigan]

How can one tell if the 5-speed in a 1980 Sports D-50 is a KM132 or a KM145? What's the difference between the two for 1980?

[pennyman1]

all 1980s are km145 - km132 did not appear until the 83 2.0.