It can be done as part of the variant changes, variant 2 for example is- I think -variant 1 but for lefties.
You can see on your frame the cuts are there, even the white line is there.
HK recommends variant alterations be done only by HK qualified gunsmiths. However, it seems like on of those things if you are responsible about it, take your time, and work carefully you could probably get it done.
Maybe others will know for sure if it is something you can easily do etc, in any case I don't have any instructions or such that would help you- other than I do know it is possible.
