I'm sure I read somewhere that someone bought a 911 front a arm but it was different to the 914. Is this so? If I found 1 for a 911 would I need to change both to balance the car?

The torsion bar spline count is different between 911 and 914. There may also be a difference in the sway bar tab. Some 911 have a circular mount, some 914 have the U-tab mount and others have no mount. Easy enough to add or change, as needed.

with all of the above and since the smallest 911 torsion bar is 1mm larger than a 914 torsion bar, using dissimilar A arms will never balance out. 1mm doesn’t seem like a lot but it’s about a 15% increase in stiffness.

Just like tires, brakes, and shocks, replace in pairs.

I've been browsing adverts and some are listing for cars up to 1972. Was there a physical change at this point? I've also checked the parts catalogue but it doesn't list a number for the arm itself.

Are you talking 914 arms? If so, my guess is that the difference would be that the 70-72 do not have U-tabs for the sway bars. I don't think the change to the new ball joint affects the A-arm in any way at all, so that's the only thing I can think of that would differentiate them.

And yes, I know that many 73+ cars did not have sway bars, and many of the ones that didn't have those also didn't have tabs. But that's the only difference I can think of...

--DD

Dave, are you sure about the early cars. All mine have tabs but didn’t come with the sway bar.

I have seen a different tab that holds the ball joint from turning between early 70-72 and later arms. Fully inter changeable. Yes, early A arms cam have sway bar tabs. Weld on tab vs tab formed from stamping of A arm.
Bruce

Late 74,75 and 76 did not come with tabs unless sway bars were ordered. All the rest should have tabs for drop links. 65-68 911's had bolt on tabs. 69-73 had tabs also. 74 911's changed to under body mount.

DD My '72 came with the tabs in place. Don't remember my '70 it's been 38 years since I've seen it.

Not sure what year 911 switched to D shaped tabs with the underbody sway bar?

1974 is when the 911 switched to the under body sway bar

Mine is may 1974 build and it does have drop links so I will need the tabs

As the 911 arms are slightly bigger, in exactly what dimension(s) i'm not sure, does the 914 brackets fit as straight bolt on as if they were refitting 914 arms.

The tabs pictured do not look big enough, and are much smaller than my rxisting ones, to bolt the droplink to.