Later clutch pack (K5 or K6 I think, and later?) is slightly longer by 2 or 3 mm. I understand the later clutch cover, therefore is also slightly different in order to clear.
What's the easiest way to tell the difference? I pulled the clutch cover on my engine, which is '72 cases, and I've confirmed has early clutch. But I also have a clutch cover in a box of parts I got from the PO. There are some definite differences, such as a more defined "lip" around the edge on the clutch cover on the engine, whereas on the "parts box" cover the bolt holes are slightly cut for the bolt head to seat down in a bit more, there's an extra flange near the kickstart shaft, and some of the ribs on the inside seem to be cut back a little. I'm thinking I have one "early" and one "late" clutch cover.
Or am I making mountains out of molehills?
Here are some pics: