The K2 came both ways with the fork caps (hence the arguments...). Mine was made 11/71, and it had them "backward" [so says the internet today] right from the crate. The K2 that came after 3/72 build changes occurred (like, no more Stellite valve guides, new 3-piece piston rings, common clutch hub with 7 plates OEM) also had the fork caps on the other way, with the gaps at the back.
...but not always, out of their crates...so, look closely at yours to see if they are marked "F". If so, that side goes to the front, and torque down the side that meets the faces flush first, then the other one. If you have the early "F"-marked ones, you might also find that they like one fork better than the other side: some were hand-finished with a flat file on one side so they were the same width as the fork leg lower.