Would be great to have N64 on the N3DS. But if I remember correctly, from what has been Posted on the RA Nightly Thread, any N64 Emu or Core, would have to be made by Scratch. Something to do with the Processor or Graphics. There is a N64 Emu in Development, but that seems like it has been scrapped since there has been no Activity on the GitHub Page for quite a while.
Would love to see if HBMAME can be Ported. There are plenty of Sources on their Page. Would give new/altered/hacked Arcade Games.