The parts book shows both. I'd go by the parts book before a generic picture in the FSM that's used as an assembly guide.
Even if the "3/4" angle" was correct,
it still isn't the straight, later housing shown in the OP's pictures. Chances are it's from an engine swap or a cracked housing and the incorrect housing got bolted on. Lot's of things happen in the 57 years since the car was built. The straight housing would work if the A/C brackets were changed to the later style.
From looking at the orientation of the 3/4' angle housing, I believe that
it would put the hose right into the A/C compressor and therefore, wouldn't work at all. Here's a pic of the 3/4" housing on a '66 Newport without A/C. Note that it tips towards the front of the car, right where the A/C compressor would be.
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The 2" angle housing is available as a Dorman replacement for under $30. Going by what I've seen, both in the field and with a little searching, the 2" angle housing would be my choice to correct the problem.
BTW, I think the 3/4" and 2" angle is the amount of offset in inches from vertical.... But that's kind of a educated WAG at best.
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