Uh, I removed my entire rear suspension. (67 250s) to refurb.

I did not know the thrust/torque arms are driver and passenger specific. Only when reading the Haynes did I see this note.

How can I tell?

The only really obvious difference is in the front. There is a half riveted circle. See pics. Should these parts face the outside of the car, or the inside of the car.

Any other ways to tell?

I can't reinstall until I know!

Thanks.

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The difference is in the orientation of the spring seats, which in your example appear to be bolted on, and can be rotated. A top view would be helpful.

I confirmed that the half riveted on pieces face IN.

1) Black parts photographed against a light background become devoid of detail; the exposure is determined by the brightest area in the pic.
2) No rivets are visible. The mount cup is resistance/spot welded to the arm.
3) The photos are all of the bottom side of the arms.