There are four main mechanical parts, the wiper motor, the crank arm, the drive link and the connecting link.
The motors for the years of interest -
3431077 1971 B VARIABLE
3431531 1972 A 2-SPEED UP TO 6/5/72
3431532 1972 A VAR-3SP
3431533 1972 BCE 2-SPEED UP TO 6/5/72
3431534 1972 BE VAR-3SP UP TO 9/1/71
3431535 1972 C VAR-3SP
3431605 1972 A 2-SPEED AFTER 6/5/72
3431605 1973 A 2-SPEED UP TO 2/1/73
3431606 1972 BCE 2-SPEED AFTER 6/5/72
3431606 1973 BCE 2-SPEED UP TO 2/1/73
3431624 1972 BE VARI-3SPD AFTER 9/1/71 BLACK CAP
3431665 1973 BE VARI-3SPD
3431666 1973 C VARI-3SPD
3431718 1973 BCE 2-SPEED AFTER 2/1/73
3431730 1973-74 A 2-SPEED AFTER 2/1/73
3431780 1974 C 3-SPEED
3431790 1974 BCE 2-SPEED
3431905 1974 A 3-SPEED
3431906 1974 BE 3-SPEED
3620877 1973 A VARI-3SPD
For 1971/1972 models
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The crank arm (23-67-76) connects the motor (23-67-98) to the drive link (23-67-79) and must have matching mechanical connections to the motor and the drive link being used.
As I discovered the hard way, the connection between the 2822289 crank arm & the 3431102 drive link (1971) and the 3431518 crank arm & the 3431515 drive link (1972) are different. The bushing on the 3431515 is wider than the one on the 3431102 which means the pin on the 3431518 crank arm is longer than the pin on the 2822289. What this means is that you need to have a matched set motor, crank arm & drive link to assemble a three/variable speed setup.
Here's a photo of the 2822289 arm and 3431102 drive link.
Here's a photo of the 3431518 arm and 3431515 drive link.
The wiper pivot connecting link (23-67-79) is the same 3431103 part for both 71 & 72 Chargers with either two speed or three/variable speed configurations. It is not the same as the E-bodies (2822291) however.
To do a period correct conversion for a 71 Charger, you need:
3431077 Wiper motor
2822289 Crank arm
3431102 Drive link
3488073 Switch (w/standard inst. panel) or 3488043 Switch (w/Rallye inst. panel)
To do a period correct conversion for a 72 Charger, you need:
3431534 or 3431624 Wiper motor
3431518 Crank arm
3431515 Drive link
3621671 Switch (w/standard inst. panel) or 3621672 Switch (w/Rallye inst. panel)
I believe you can install a 71 setup on a 72 or vice vesa as long as all three parts (motor, crank arm, drive link) are swapped together but the connector on the dash harness is different for the switches between the two years. Nacho can probably confirm or correct this.
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