Here the differences, side by side

Left is 71, right is 72/74

Since 71 is blurry I overwritte the colors at a side of wire code

71s got two plugs, 72/74 got one piece larger plug.

switch can be indexed diff on diagrams but differences are noticeable

71 switch is also larger diameter than laters.

this section is the ONLY difference betyween 71 and 72/74. Bulkhead disposition is exactly the same, same as wiper harness.

applies the same to 3/var speeds.