A bit more - back in The Day, the crank halves were sold individually.
The upper came sans studs, and with a blank area where the serial number goes.
At the shop, you stamped in numbers manually.
The uppers can be prone to breakage of the area that the kick shaft end hold-down thingy is. An 8mm bolt screws in there, and that can break off - rendering the upper useless. Got two of them under the bench right now.
Unless you're being persnickety about being "correct", no need to try and find K3 or K7, or whatever - only in the few states that title on the engine number will it matter.........it's irrelevant otherwise, all the 5-speeds are the same.