I have this NOS power steering pump that's in its original box. The part number marked on the box is 3685611
I have had no luck searching that number to determine its application. I'm thinking it's maybe for a Truck?
The pulley on it has a 6-3/4" diameter.
Someone before I bought it, wrote on the box cover "Rare Fairbanks Pump". To me it's a Federal Pump.
Does anyone know what its for?

looks like a federal pump to me.

It' is a Federal pump.
With that mounting bracket on it, was used from 1969-72. big block engines.
Since it's a "solid" pulley, and not a three spoke one, it could be a 426 Hemi pulley.
If it is, good score.

Well, I have figured it out. It turns out to be of all things a Slant 6 power steering pump set up.
Here it the same deal for sale on ebay. I also have the same "funky" looking pulley that goes on the crank.

https://www.ebay.com/itm/Mopar-225-...lleys-Dart-Cuda-B-A-E-Body-/123655721255

Maybe I will remove the brackets and pulley and just sell the Federal pump separately. Probably worth more that way.

I believe I pulled a similar pump/pulley off a 1968 383. There was also a copy-cat federal pump, I think it was a TRW? One had adjustable or variable assist based on rpms, I don't remember which. I found it was hard to find a spoked pulley that wasn't bent which is why I swapped to the solid one. After several federal pumps puked their guts past 6000 rpm, I ripped it all off and went with a saginaw.

EDIT: If anyone buys cores for this stuff in the PA/NY/NJ area, send me a PM.

If 3/8 threaded shaft it is Federal. Bracket is not BB. Big block is one piece that attaches to Water Pump.