"You would have to investigate to see if there is any difference in the stock set-up of the '72 from the '73."
It changed on the swinger but that may only be because they ommited the vent window in 73. Since duster didnt have the vent window it probably was the same regulator until 74.
Like I said, 74 was not compatible when I compared it to my 73 guts. I wanted to save the windows for spares but as you found out, the holes in the glass are not the same.
Instead of cutting and welding the new regulator, could the motor portion be made to fit the original regulator? Might be less work in the end.