Okay guys, I'll testify to the nightmare that is a blower motor replacement. It might be worse because I've worked on it an hour or so at a time. I recommend dedicating a day to it so that everything's fresh in your mind when you're putting it back together. Also, as dorky as it sound, I recommend putting each group of screws in a baggie and labeling it. I did not do this. :(

It at the wiring point now. IPD's instructions say
"Install the yellow wire which was previously located in pin #3 of the old fan switch plug into pin #6 of the new switch plug. The opposite end of this wire is connected to fuse #2."
"Use a new wire and connect it from pin #5 on the fan switch plug to terminal #87 on the AC relay."
"Use a new wire and connect it from fuse #3 to terminal #86 on the AC relay."

The switch plug is not numbered at all! How do I know where pin #6 and pin #5 are?
I found the only unconnected terminal on the back of the switch (I think) and used that for the yellow wire in step 1.

What does the relay wiring do? Is it necessary for a 1975 164E?

Thanks a million!