Originally, the rear motor mount was made of steel and had 4 bolts in the top. ¹⁾
Later it was made of aluminum and prone to cracking. The steel mount will never crack.
The first aluminum mount had 4 bolts in the top. Later the mounts had only 2 bolts.
Aluminum mounts are going to crack. If you have a brand new replacement mount in hand right now, it will crack.
Should your mount be a steel one, then it is worth installing. But, the cracks do not present a real problem though.
That is the good news.

Sometimes the mount cracks all the way across as in the pics below.
Whilst many of them tend to crack, some only crack so far and then stabilize. ²⁾
Unless it's completely cracked through or flexing like mad, you can run it and monitor whether or not it gets worse.
So it's not necessarily a problem that has to be fixed depending on how badly cracked it is.
However, it does reduce vibration to repair or replace.

And even if the aluminum mounts are installed correctly, they will still crack. They seem to crack worse after welding. ³⁾
It may be best to score a 57-60 steel mount (a 52-56 k model mount will work too if you ain't got a kickstart) and cut it to mimic the -67 mount.
You can try to have the crack welded as in the pics below.
You can also replace it with an aftermarket mount. Pingel has a high reputation as an aftermarket alternative.
See Pingel Rear Motor Mount in the REF section of the Sportsterpedia.
The heavy aftermarket works but it takes up more room and you gotta screw around with the lower oil tank mount if you're working on a 70-78CH.

This one is cracked all the way across.
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This one is only cracked for a small distance.
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This one from a 68 XLCH has been welded.

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