Factory markings on the left outside wall of the recv'r?
If cut, shortened and welded, the markings won't match back up even to be recut through the welded area.
The distance from the front 'ring' to the thumb cut (if there is one) is shorter on the K and the factory marking starts closer to the ring and ends closer to the thumb cut because of the lack of space. I think the letter size may be different/smaller but I'm not so sure of that.

Markings can be cut by hand but magnification will usually give them away as done so. Roll stamping and stamping in general leaves a different look than graver cut or machine cut lettering.

I don't know enough (anything!) about the records of the ser#'s and what's available & what isn't to verify in that manner if it is.

I have a Mauser carbine w/a K action in 6.5cal. Certainly is a different feel to the little gem when handling it.

Just some thoughts.