Need help!!! 1965 power steering nightmare

He's not missing the return line nipple on his steering box. It's right there in the pic. The high pressure fitting is in place and intact on the box, too, and if the high-pressure line he winds up using has a male end, the fitting on the box can simply be unscrewed and removed, then the male end of the line screws right in -- as described here.

P/S box interchange is '62-'72 A- and B-body.

A '65 would have had either a Thompson or a Saginaw pump, but this is a later-type Saginaw pump. Brackets for the early-type Saginaw pump might or might not accept this later-type pump, I don't recall. Brackets are different for Saginaw vs. Thompson pump, and in some cases with/without Air conditioning. Later brackets are a no-go; they'll put the pump right into the side of the battery (later cars have wider engine bays). The high-pressure line from pump to box differs for Saginaw vs. Thompson pump, too. You have to have the same size return line nipple on pump and box. Large and large or small and small. The nipple on the box is easily changed and not too hard to get hold of if you wind up needing the smaller size with whatever pump you end up using. The pump shown in post № 6 of this thread has a pulley on it that is correct for at least pre-'67 cars with factory A/C (they got the cone-shaped pulley; non-A/C cars got a more or less flat pulley, also used with dealer A/C).

The P/S pump belt drive is either an accessory sheave that bolts to the front of the crank pulley (all years same), or you can use the heavy-duty 3-groove truck crank pulley.