can a early ball joint be - physically - installed onto a late strut?
>>i assume yes

can a late ball joint be - physically - installed onto an early strut?
>> i assume no

i guess i should just slide both ball joints out of the struts and see what i have. i think i'll need to replace the late strut with an early strut because i think i have early ball joints - i know i have early style calipers.

I just realized, or should I say Mike Hyde pointed it out, that I have 914-6 struts and a '74 so I guess I also have the wrong ball joints.

I'm using the aluminium Brembo caliper.

Early struts have a through bolt with threads.

Late struts have a pinch bolt with a nut on the threaded end.

Early ball joints have a C shaped groove for the through bolt.

Late ball joints have a V notch for the pinch bolt.

The Ball joints can not be safely or correctly interchanged. I would need a pic of the other sides of the struts to tell what you have.

Your lower pick looks as if there is a hex head on the back side of the fastener. Thus, both would be old style and the bottom pic shows a bolt threaded into the threaded end with the top pic showing a long bolt with a nut on the end, which is common if the strut threads are stripped.

From what I see in the pictures, the one on the left is the old (early) type with the bolt. The picture on the right looks to be a wedge pin (late) type. The base on early struts has a cut sliced out of it to the center. Late struts have a solid base with round holes and no threads on one side.

doc - you are exactly right. was was sort of figuring this out when scottyb pmed me with exactly what you have written.

i am ok with a long bolt used for this reason, and relieved that all else is early style, not in need of swapping out any parts -whew

Both struts have split bottoms so... Both struts are early style. You're fine.