On my 65 I have the 2 speed wipers with a 2 speed switch, and am looking to replace the washer pump. I noticed when comparing my existing unit to what's in the MU catalog, it appears I have the pump with the single speed wipers. I'm assuming these aren't interchangeable correct?

 

no they are not interchangeable. most 65 mustangs had a one speed so there's a very good chance that's what you have

 

Well, the pump only needs +12V and ground. Find the wire coming from the switch that's supposed to run the pump, and connect the pump to that. If you're in the market for a new pump anyway, NPD has a washer pump for a 66 with 2-speed wipers.

National Parts Depot catalog number: 17664-2A $42.50

 

Most, but not all. I know they were part of the visibility group, along with adjustable driver side mirror, and a day night mirror.

As for the other question, did you try other places like Virginia Mustang or C. J. Pony?

 

I can't say with any certainty, but I think the car came with the visibility group. It has the adjustable side mirror and day/night mirror. Its' whether or not some PO added these features at a later date.

I have not checked with any other suppliers as of yet.

Also the 2 speed pump I've seen pictured in several places has 2 wires emanating from it. I assume one was connected to the switch and the other to a ground, possible attached to the mounting screws. Correct?

 

It doesn't matter on a 65. The same pump was used either way. If MU says otherwise, they really need to correct their listings. Glazier/Nolan has the pumps listed correctly, and they stock the pump you need.